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Bulletin No. 19. Agros.47.
U. S. DEPARTMENT OF AGRICULTURE.
DIVISION OF AGROSTOLOGY.
[Gran tin tt Forage Plant I nTestigation*.]
The Structure of the Caryopsis of Grasses with reference
to their Morphology and Classification.
BY
P. BE VE RIDGE KENNEDY, Ph. D.
PREPARED UNDER THE DIRECTION OF F. LAMSON-SCKIBNER, AGEOSTOLOGIST.
, WASHINGTON:
GOVERNMENT PRINTING
1899.
OFFICE.
LETTER OF TRANSMITTAL
U. S. Department of Agriculture,
Division op Agrostology,
Washington, D. G., May 4, 1899.
Sir : I have the honor to transmit herewith and recommend for pub-
lication as Bulletin No. 19 of this Division the manuscript of a report
on the structure of the caryopsis of grasses, ordinarily termed the grain
or seed. This report, prepared by Mr. P. Beveridge Kennedy, by special
authorization through the Agrostologist, contains much of histological
interest, but is of special value on account of the important facts brought
out in the investigations relative to the morphology and classification
of grasses. Mr. Kennedy was formerly assistant chemist in Toronto
University, Canada, and for the past three years has been studying at
Cornell University, devoting special attention to the investigation of
grasses.
Eespectfully,
F. Lamson-Scribner,
Agrostologist.
Hon. James Wilson,
/Secretary of Agriculture.
3
INTRODUCTION.
The fruits and seeds of plants present characters which are less sub-
ject to variation than any of the other organs or parts. In consequence,
these characters are of the highest importance in studying the classifi-
cation and relationships of plants. They are employed in separating
the larger groups, and in some cases ordinal characters are based upon
them; and within many families the fruit affords the best differential
characters for the separation of subtribes, and even genera. To what
extent the fruit, or caryopsis, of grasses may be employed in determin-
ing the relationships of the various tribes and genera is to some extent
indicated in the following paper. Enough is presented to show that
the characters possess great value in this connection and clearly empha-
size the interest and importance of a knowledge of the structure and
morphology of the caryopsis of the different tribes of Gramineae — a
subject here treated for the first time in the English language.
The structure of the fruits of the cereals has been investigated to
some extent at a number of the agricultural colleges and experiment
stations, but the cultivated grains only represent three of the thirteen
tribes of grasses.
F. Lamson-Scribnek.
4
CONTENTS.
Page.
Historical review 7
Summary 13
General description of the fruit 13
The scutellum 14
The epiblast 15
The plumule-sh eath 19
Therootsystem , 20
Lateral buds 20
The fibro- vascular system 21
Homology of the parts of the embryo 23
Detailed descriptions of fruits 26
Tribe Maydeaj *. 26
Tribe Andropogoneae 27
Tribe Zoysiete 28
Tribe Tristeginese 28
Tribe Panicese 28
Tribe Oryzese 29
Tribe Phalaridese ', , 30
Tribe Agrostideae 30
Tribe Aveneae 31
Tribe Chloride* 32
Tribe Festuce® 33
Tribe Hordeae 33
_ Tribe Bambuseao 35
Relationship and systematic connection of the tribes 35
Bibliography 38
Explanation of plates 42
5
ILLUSTRATIONS.
Plates I-VIII. Structure of the Caryopsis of Grasses
6
THE STRUCTURE OF THE FRUITS OF GRASSES WITH REFERENCE TO THEIR
MORPHOLOGY AND CLASSIFICATION.
HISTORICAL REVIEW.
The first writer to mention the fruits of grasses from a morphologi-
cal point of view was Malphigi, 1 who described the embryos of Triticum
and Avena in 1687. He regarded the scutellum as representing the
cotyledon. Nothing further was written concerning the embryo of
grasses for a hundred years, when Gaertner 2 described it in 1788. He
studied a considerable number of species, especially in regard to the
scutellum. The name " scutellum " was first used by him. He
regarded the "vitellus" as a transition between the endosperm and
the cotyledon. A. L. de Jussieu 3 in describing the grass fruit used the
term "lobus" implying the cotyledon.
In the year 1808 Poiteau 4 concluded that the sheath in the embryo,
called " vitellus " and " scutellum " by Gaertner, is a true cotyledon.
He decided that the epiblast must be the rudiment of a second cotyle-
don, because of its position opposite to the cotyledon or scutellum.
Kichard 5 in the same year presented the view that the scutellum
originates from the lower part of the radicle, and that therefore the
scutellum is a lateral protuberance of the radicle. By imagining
the plumule raised in such a manner that it stands at right angles to
the long axis of the scutellum, he constructed an homology with the
embryos of the Naiadacece, Alismacece, Hydrqeharidacece, and Nympha-
cece. The word epiblast originated with Richard. He regarded it as
a continuation of the root sheath, basing his opinion on a section cut
obliquely through the embryo of Oryza.
In 1809 Kirbel 6 compared a number of embryos of the grasses in the
resting and germinating stages with those of other monocotyledons.
He believed that the scutellum represented a cotyledon and that the
epiblast was a reduced cotyledon. In another work 7 Kirbel regarded
1 Opera omnia. 1687.
* De fruotibus et seminibns plantarum. 1788.
3 Genera plantarum secundum ordines naturales disposita. P. 28. 1789.
4 Memoire snr l'embryon des Graminees, des Cyperacees et du Nelumbo. 1808.
6 Analyse des embryons Endorh. on. Monoc. et part de cel. d. Gr. 1808.
6 Elements de Physiologic vegetable, r. I. 1809.
7 Examen de la division des veg<!taux en Endorhizen et Exorhizes. 1810.
7
8
the plumule-sheath as belonging to the cotyledon, but in 1815 returned
to his former view. Treviranus 1 opposed Richard's view and regarded
the scutellum as a cotyledon. He speaks of the scutellum as enlarging
itself the length of the seed and taking on a yellowish color, which is
certainly not the case. Turpin 2 agreed with Mirbel that the embryo
has two cotyledons. According to Cassini 3 the embryo of the grasses
is composed of an axis, a cotyledon, one or two radicles, a plumule, and
one or two " carnodes." His " cotyledon " is the. plumule-sheath, while
the "carnode," a name for the scutellum, he regards as a protuberance
of the radicle. Easpail 4 compared the fruit and the flower. He
believed that there was also an homology between the embryo and the
culm. On examining the cotyledon he discovered a large nerve, join-
ing the two nerves of the plumule-sheath at the base. From this he
concluded that the scutellum is homologous to the peduncle of the
aborted flower in the spikelet and to the sheath of the culm-leaf. He
compared the plumule-sheath with the two-nerved palet in the spikelet
and to the first leaf of the vegetative bud, and the endosperm to the
flowering glumes of the spikelet and to bracts on the culm.
Dr. 0. A. Agardh 5 in 1826 compared a longitudinal section of the
embryo of Buppia with the grass embryo and fruit, and found a great
similarity between them. He regarded the entire endosperm of the
grasses as the cotyledon, and the scutellum as a covering of the same.
This, however, is impossible, as the scutellum never surrounds the
endosperm. Bernhardt believed that a cotyledon must, aside from its
function of nourishment, also act as a protective organ to the young
leaves. He therefore regarded the plumule-sheath as a cotyledonary-
sheath and the scutellum as a cotyledon. Bischoff 7 also believed that
the scutellum and epiblast are two cotyledons. He regarded the
caryopsis as having an embryo with alternate cotyledons, without how-
ever giving any special grounds for this opinion. M. J. Schleiden 8
was the first to study the development of the grass embryo. Accord-
ing to him the scutellum and the plumule-sheath together form the
cotyledon. He regards the epiblast as an outgrowth of the cotyledon,
since it is connected with the main axis lower down than the cotyledon
1 Von der Eutwickelung des Embryo und seiner Umhiillungen im Pllanzen-Ei.
1815.
2 Memoire sur l'irrflorescence des Graniin£es. Ann. d. Mus. d'hist. Nat. 1819.
3 L'analyse de l'embry on de Graminees, Jour, de Physique. T. 91. 1820.
4 Sur la formation de l'embryon dans les Grarainees. Ann. des Soc. Natur, Series 1,
vol. 4, plates 13-14, 1824, 271-290. 1824.
6 Uber die Eintheilung der Pflanzen nach dem Cotyledon und besonders iiber den
Samen der Monocotyledonen. 1 Nov. Act. C. B. C., T. XIII, P. I. 1856.
6 Ueber der merkwiirdigsten Verschiedenbeiten des entwickelten Pflanzenembryo.
Linnaea. 1832.
' Lehrbuck der Botanik I. 1834.
8 Einige Blicke auf die Ent wickelungsgeschichte des vegetale Organ bei den Phan.,
Wieg. Archiv. Ill, I. 1837.
9
itself. Adrien de Jussiea 1 differed from his father in the interpreta-
tion of the parts of the embryo, believing that the scutellum is not a
true cotyledon but only a lateral appendage of the axis which resembles
one. This view has been held by many up to the present time. Kegel *
considered the plumule-sheath the true cotyledon aud the scutellum
first as a stipule and again later as a bract from which the plumule
arises laterally. In the same year Reisseck 3 advanced the opinion
that the plumule-sheath is an axillary bud and that the cotyledon
(Samenlappe) is an organ of the aborted terminal bud and the protect-
ing leaf of the plumule, and that the epiblast is united with the
cotyledonary-sheath, which is evidently also a part of the cotyledon.
Lestiboudois 4 regarded the plumule-sheath as the cotyledon, but con-
sidered the scutellum of no significance, because only the former is
traversed by fibrovascular bundles, hence resembling two leaves grown
together.
Hofmeister 5 interpreted the embryo in different ways, describing the
development of Zea. He called the scutellum the cotyledon and the
plumule-sheath a part of it. A few years later, in another work, 6 he
compared the so-called scutellum of the embryos of Zea and Andropo-
gon sorghum with the first leafless structures of Zostera. Demoor 7
investigated a large number of the fruits of grasses in the mature
stage, and also their development. He regarded the scutellum as the
true cotyledon of the grasses, and the plumule-sheath not as represent-
ing the ligule, but as a sheath of a primordial leaf. This would not,
however, correspond to the alternating arrangement of the leaves of
grasses, a difficulty which he bridges over by citing that there is no
opening of the sheath in Meliea uniflora because of the growing
together of the two margins of the leaf. He admits, however, that he
has not been able to observe this. J. 0. Agardh 8 speaks of the embryo
as sometimes presenting a thalloid form. Schacht 9 considered the
scutellum as the cotyledon, the plumule-sheath as the first leaf, and
the epiblast a part of the cotyledon.
Hofmeister, 10 writing again concerning the grass embryo, stated: "I
still regard the scutellum of the grasses and the analogous structure
1 Sur les embryons monocotyle"dones. Coinpt. Rend, des Soc. de l'Acad. des Sci-
ences, 9 : 15-31. 1839.
s Beubachtungen iiber den Ursprung der Stipeln. Linnaea, 17. 1843.
3 Monocotylischer Embryo. Bot. Zeit. 1843.
4 Phyllotaxie anatomique, Ann. des. sc. naturelles, ser. Ill, 10 : 15. 1848.
6 Die Entstebung des Embryo der Phanerogamen. 1849.
6 Zur Entwickelnngsgesehichto de» Zostera embryo. 1852.
'Note sur l'embryon des Graminees. Bull, de l'Acad. roy. des Sci. de Brux. 1853.
8 Theoria system, plant. 1858.
9 Lebrbuch der Anatomic nnd Physiologie der Gewachse. 2, 1859 und das Mikro-
scope, 224. 1862.
10 Keue Beitrage zur Kenntniss der Embryobildung der Phanerogamen Abband.
der konigl. sachs. Gesellschaft. d. Wien. 1861.
10
of Zostera as an outgrowth from the axis, and not as a leaf." In this
he agrees with Adr. de Jussien. A. Gris, 1 studying the embryo of Zea
from a physiological standpoint, also regarded the cotyledon as a lat-
eral expansion of the axis, modified iu such a manner as to become the
principal absorbing organ of the embryo.
Dnchartre 2 stated that the embryo is remarkable in having an oval,
flat, or slightly curved, bud-like expansion at its base, called by Gaertner
the " scutellum." This organ directly adjoins the endosperm by its
dorsal face. In front of it is another shoot, which Richard- calls the
"Waste." Le Maout and Decaisne 3 regarded the scutellum as a
cotyledon, which is often split along its outer face, showing the rad-
icle and plumule. The plumule is conical and composed of one to four
primary convolute leaves. They regarded the plumule sheath as the
first leaf of the plumule. Sandeen 4 investigated a large number of
ripe embryos and concluded that the scutellum is a thallus formation
and that the plumule is a protuberance of the axis.
Sachs 5 regarded the scutellum as an outgrowth of the axis beneath
the cotyledon and the plumule-sheath as the cotyledon, enveloping the
whole plumule like a mantle. Hanstein 6 studied the development of
Brachypodium from the embryo sac to its maturity. He regarded the
scutellum as a leaf and a cotyledon, and both the plumule- sheath and
the epiblast as trichomatic projections. This is difficult to imagiue.
Van Tieghem 7 reviewed the subject, illustrating the parts of the
embryos of Triticum astivum, Hordeum vulgare, Avena sativa, Phalaris
canariensis, Zea mays, and Andropogon sorghum vulgare, briefly stating
his own objections to the views previously held. He considered that
the scutellum and plumule sheath together represent the cotyledon,
which has at its opposite side a small protuberance called the lobule or
epiblast. Owing to the presence of two vascular bundles in the
plumule-sheath, he calls it a double stipule united at the margins, and
homologizes the scutellum and plumule sheath with the leaf and ligule.
Hegelmaier 8 discussed the grass embryo from its developmental
history, giving excellent figures of Triticum cestivum. He also noted
the occurrence of secondary roots in Coix, Hordeum, Secale, Avena,
Triticum, and other genera, concluding with Van Tieghem that the
1 Recherches anatomiques et physioloques sur la germin. Ann. des Sci. natnrelles,
ser. 5, 2 : 1864.
a Elements de Botanique. 1867.
3 Recherches anatomiques et physioloques sur le germin. Ann. des Sci. natnrelles,
ser. 5, 2 : 1864.
4 Bidrag till kaenn ed omen om Grasembryots byggnad och Utweckling. Acta
Univers, Lnndens, 1868.
6 Lehrbuch der Botanik, 474. 1868. Eng. Trans, and revision by S. H. Vines, 1882.
6 Die Entwickelung des Keimes der Monocot. and Dicot. Botanis, Abhand, 47.
1870. Taf. 14, figs. 11-21; Taf. 15-18.
' Sur les Cotyledons des Graminees. Ann. des Sci. naturelles, series 5, 15 : 723-276.
1872.
"Zur Entwickelungsgeschichte monocotylischer Keime, etc. Bot. Zeit. 1874.
11
scutellum and plumule-sheath together correspond to the cotyledon of
the other monocotyledons. A. Stephen Wilson 1 held that the cotyle-
don of the grasses had not yet been correctly interpreted, and that
the morphological interpretation lay in whether the two vascular
bundles of the plumule-sheath represent the middle nerves of two
leaves or whether they only occur to strengthen the organ. In com-
paring this with the leaves in the terminal bud of the rhizome of
Agropyron repens he found a difficulty, owing to the latter being many-
nerved. He believed that the scutellum certainly has the function of
a cotyledon and is a nourishing organ for the embryo at germination,
but whether the plumule-sheath is also a nourishing organ is left in
doubt.
Gordon 2 studied the morphology of the inflorescence. He says that
the node-like swelling at the base of the plumule- sheath occurs very
generally in the grasses. It appears to be a part of the node, but in
reality is only a circular swelling at the base of the closed sheath.
The proper node lies underneath this swelling. The plumule-sheath
must exercise a certain pressure on the axis, and if axillary buds are
present this pressure must have a certain influence on the plumule.
The author speaks of the well-known organ, which denotes the origin
of a branch, and which is looked upon by most morphologists as a two-
keeled simple "Vorblatt" (prophyllum), with its back turned toward
the main axis. The axillary shoots in Zea, Tripsacum, Coix, and many
others make a cavity or groove in the culm, showing that they have
developed under pressure of the sheath. The tissue at the base of the
culm remains soft and capable of growth for a long time as a basal
vegetation point. In other grasses, such as Arundo and Phalaris, the
axillary shoot does not press itself into the culm. In these the grow-
ing point breaks through the sheath to the light. In Arundinaria the
sheath soon dries up and the growing point has nothing to hinder it.
Attempting an analogy between the fruit and the spikelet, he con-
cluded that the plumule-sheath represents two leaves grown together.
Certain Graminece, he says, have one or two buds in the axil of the
plumule sheath, each with a prophyllum.
Warming 3 regards the scutellum as the cotyledon and the plumule-
sheath as an independent leaf, the latter because an internode is occa-
sionally found. Klebs 4 agrees with Van Tieghem. Hackel 5 believes,
as does Warming, that the epiblast is a rudimentary second cotyledon.
' On the envelope of the plumule in the grass-embryo. Trans, and Proo. of the Bot.
Soc. of Edinburgh. 13 : 457. 1879 (with plate).
2 Etudes morphologiques sur la famille des Graminees. Revue des Sci. naturelles,
Montpellier. 1879.
3 Handbog i den Systematiske Botanik. Trans, by Potter. 1895.
4 Beitrage zur Morphologic und Biologie der Keimung. Untersuch aus d. Bot.
Institut der Lnbingen.
6 Echte Graser. Engler und Prantl. Pflanzeufamilien, 2 : 1887. 2. Eng. Trans,
by Scribner and Southworth. 1890.
12
Kegarding it as a cotyledon explains the peculiar position of the first
leaf over the scutellum. Many authors, he says, regard the plumule-
sheath as a part of the cotyledon, surely an incorrect idea. Lermer
and Holzner 1 in an exhaustive histological treatise on Hordeum vulgar e
describe in detail the different parts of the fruit. They regard the
scutellum as a shield-like expansion of the hypocotyl, acting as a
special absorption organ, and the plumule as composed of four leaves
inclosed in a plumule-sheath, but attempt no interpretation of the
latter view.
Bruns 2 has investigated the grass embryo chiefly from a systematic
point of view. He describes and figures a large number of genera of
each of the tribes. He regards the scutellum as one cotyledon, and
the epiblast as a second, much reduced on account of the great
development of the former. He considers it of no consequence from a
systematic standpoint whether or not the scutellum and the epiblast
are regarded as two cotyledons, provided it is granted that they
represent two leaves, as the cotyledons are the first two leaves placed
together. The plumule sheath is the thickened first leaf of the plumule
especially adapted for protecting the young leaves. It has no blade, a
common characteristic of the lower leaves of grasses. Schlickum, 3 in
comparing the cotyledons of the monocotyledons, says that when the
cotyledon has assimilating functions to perform its lamina displays a
differentiation into a nutrient portion, the haustor, and a conducting
portion, the conductor. In the grasses the conductor is very rudi-
mentary or entirely suppressed, while the scutellum is transformed into
the haustor, which bears no resemblance to a foliage leaf. The epiblast
is probably an outgrowth of the coleorhiza. When the cotyledon does
not emerge above the soil its function is to take up, by means of the
haustor, the nutrient substances present in the endosperm, and to pro-
tect the rudimentary leaves by the formation of a more or less
developed cotyledonary sheath.
Finally, Celakovsky 4 reviews the work of previous investigators and
criticises them especially in regard to the homology of the epiblast
and plumule-sheath. He believes that the true morphological nature
of the parts can only be determined by investigating along many dif-
ferent lines, and if all these lines point toward the same conclusion,
then surely it must be the correct one. The writer investigates the fruit
according to the four following lines: (1) Ontogeny; (2) taxonomy;
(3) anatomy; and (4) progressive and retrogressive metamorphoses.
He then attempts to find out where the scutellum and plumule-sheath
are joined at the base; where they separate; and whether the plumule-
'Beitrage zur Kenntniss der Gerste. Munchen, 1886. Extract by Brown and
Morris Chem. Soc. Jour., vol. 57. 1890.
3 Der Grasembryo. Flora, 76 : 1892.
3 Morphologischer und anatomischer Vergleich der Cotyledon und ersten Keim-
blatter der Keimpflanzen der Monocotyledon. Bibl. botan. Heft. 35. 1896.
* Uber den Homologien der Grasembryo. Bot. Zeit., Sept. 1897.
13
sheath is inserted directly over the scutellum; and, finally, how the
insertion of the plumule-sheath becomes separated so far from the,
scutellum through the elongation of the axis. He also homologizes the
grass fruit with Smilax, Potamogeton, Ficus elastiea, the mosses, and
the leaf of the grasses. He regards the scutellum as the blade of the
cotyledon, and as being homologous with the blade of the leaf. Over
the scutellum is situated the plumule- sheath which is homologous to
the ligule. The epiblast is the blade of an opposite second cotyledon.
SUMMARY.
The most important views of the different authors may be summed
up as follows :
1. The scutellum is the cotyledon ; the epiblast a second independent
leaf; the plumule-sheath a third leaf; while the first true leaf is the
fourth lateral appendage of the embryo. — (Malphigi, Mirbel, and
Poiteau.)
2. The scutellum and the epiblast together form the cotyledon, the
plumule sheath a second leaf, and the first true leaf becomes the third
lateral appendage of the embryo. — (Schleiden, Shacht, and Decaisne.)
3. The plumule-sheath represents the cotyledon, the scutellum and
epiblast being only expansions of the axis or of the radicle; and the
first true leaf then becomes the second lateral appendage of the
embryo. — (Eichard, Adr. de Jussieu, Lestiboudois, Hofineister, and
Sachs.)
4. The scutellum is the central portion of the cotyledon, the epiblast
an opposite appendage of it, and the plumule-sheath an ascending part
in the form of a protective organ ; the first true leaf then becomes the
second lateral appendage of the embryo. — (Gaertner and Mirbel, at a
certain time.)
5. The scutellum and the plumule-sheath together represent the
cotyledon, and correspond to the blade and ligule of the culm-leaf; the
epiblast is a protuberance of the cotyledon on the opposite side. — (Van
Tieghem and Klebs.)
6. The sixth view is the same as the fifth, with the exception that
the epiblast represents a second cotyledon opposite the scutellum. —
(Celakovsky.)
7. The scutellum is one cotyledon and the epiblast is the other, the
plumule-sheath being the first leaf of the plumule. — (Bruns.)
GENERAL DESCRIPTION OP THE FRUIT.
The embryo of grasses stands isolated from those of other monocoty-
ledons in possessing two peculiar structures, the epiblast and plumule
sheath. The following investigations were undertaken to determine
the morphological significance and taxonomic value of these structures
in the different tribes. Owing to the difficulties met with at the outset
14
in securing a suitable method, the work is not so complete as at first
anticipated. 1
The fruit of the Qraminece was described first by Mirbel under the
name "cerium" and rechristened later by Eichard "caryopsis."
Its contents at maturity consist largely of endosperm and embryo,
the tissues of the nucellus, ovule, and ovary being almost completely
displaced. The only remnants of the nucellus which are recognizable
in the ripe grain are the empty cells which spring from the funiculus,
and the epidermis of the nucellus, which is continuous as a very attenu-
ated layer of cells around both endosperm and embryo. Of the walls
of the ovary only the inner one persists as a double layer of cells form-
ing the testa or true coat of seed. Within the nucellus are one to four
layers of cells with highly cuticularized walls. In section they are
somewhat rectangular in form and constitute the gluten cells which
contain the closely packed aleurone grains.
Lying between the starch-containing portions of the endosperm and
the embryo is a comparatively thick layer of compressed cells belong-
ing to the scutellum. They are for the purpose of dissolving the starchy
material of the endosperm during germination. The endosperm con-
sists of thin- walled cells packed closely with starch granules, embedded
in a fine mass of proteid material. These starch-containing cells each
possess a nucleus which is not easily recognized.
The embryo is situated laterally and at the base of the seed. It is
differentiated into the scutellum, the plumule, the radicle, and fre-
quently the epiblast. The plumule is surrounded by the plumule-sheath,
which sometimes has a slit-shaped opening on the side opposite to that
of the scutellum. The plumule sheath is composed of a vegetation
point and several layers of leaves. The radicle is inclosed in the lower
part of the embryo, and at germination, before making its exit, must
break through a protective mass of tissue, the coleorhiza, so called
because it forms a kind of sheath around the radicle. Secondary radi-
cles frequently occur iu the mature and resting embryo. They arise in
the axis usually just below the plumule.
The vascular system may be traced down into the primary radicle,
and also into the scutellum, plumule-sheath, and plumule.
THE SCUTELLUM.
The name " scutellum" has been given to the cotyledon of the grasses
because of its resemblance to a little shield. It has for its object the
protection of the plumule and the absorption of nutrient materials from
the endosperm.
1 The author wishes to express his thanks to Prof. W. W. Rowlee for many helpful
suggestions during the progress of the work; also to Profs. F. Lamson-Scribner and
W. J. Beal for much valuable material, and to Prof. F. C. Harrison, of the Ontario
Agricultural College, at Guelph, Canada, and to Messrs H. E. Carveth and O. Shantz
for aid in the discovery of a method.
15
Observing a cross section of any embryo, one sees that the scutellum
surrounds the plumule like a sheath. In Zea (figs. 4 A-F, PI. I),
Andropogon (figs. 10 A and B, PI. II), and others the plumule is almost
completely surrounded by the scutellum, so that only a narrow opening
may be seen. A longitudinal section of Andropogon saccharatus (fig. 9,
PI. II) shows the scutellum so completely surrounding the plumule that
it appears as if an epiblast was present. By observing a cross section,
however, it is seen that the margins of the scutellum surround the
plumule with the exception of a small slit (fig. 10 B, PI. II). At a point
toward the apex of the plumule sheath the scutellum bears a protuber-
ance which projects over the plumule. This is especially distinct in
Lygeum (fig. 25, PI. IV), Lolium (fig. 75, PI. VIII), and Ammophila (fig.
42, PI. V). This part has been called the cotyledonary sheath (c. s.) to
distinguish it from the plumule- sheath (pi. sh.).
At the base of the scutellum there is another protuberance in many
embryos, such as Avena (fig. 44, PI. V), Triticum (fig. 69, PI. VII),
Anthoxanthum (fig. 29, PI. IV), Uniola (fig. 61, PI. VII), Bulbilis (fig.
58, PI. VI), and Beekmannia (fig. 60, PI. VI). Sometimes a deep cleft
occurs, appearing as a separation of the radicle. In some embryos the
scutellum has a distinct sheath and a blade. A striking example of
this may be seen in Avena (fig. 44, PI. V), Spartina (fig. 53, PI. VI), and
Zizania (fig. 22, PI. III).
The attachment of the scutellum to the axis varies considerably in
different embryos. Desmazeria (fig. 63, PI. VII) and Anthoxanthum
odoratum (fig. 29, PI. IV) have the attachment directly at the base
of the plumule. In others there is a lengthening of the axis with the
attachment at the base, leaving a very small proportion of the embryo
to represent the hypocotyl: Zizania (fig. 22, PI. Ill), Homalocenchrus
(fig. 28, PI. IV), and Spartina gracilis (fig. 53, PI. VI).
The scutellum has at every point where it comes in contact with the
endosperm a layer of peculiar oblong cells called the epithelial layer.
Sachs regards it as corresponding to the somewhat similar layer found
in the cotyledons of the palms, and to the young epidermis of Bicinus
and many other seeds. The scutellum, therefore, may be regarded as
part of the cotyledon.
THE EPIBLAST.
The peculiar organ, the epiblast of Richard, situated opposite to the
scutellum, is not very well understood. Its occurrence in the Oraminem
is of much greater frequency than is generally supposed. Warming 1
describes the fruit of the grasses, but does not mention the epiblast.
He figures a fruit of Avena sativa, but does not represent the epiblast,
which is always present and quite distinct. Van Tieghem 2 speaks of
the existence of a second cotyledon in a dozen or less of the genera of
1 Warming and Potter. 1895.
2 Comptes Rendus neb. Lean. l'Acad. des Sci. 124 : 1896 and 1897.
16
the Oraminew. Unlike the scutellum, the epiblast has no vascular
system, and on this account much dispute has arisen over its morpho-
logical nature. This, however, is no proof against its leaf nature, as
there occur many instances of reduced organs without flbrovascular
systems.
Although the epiblast is usually very small in comparison with the
scutellum, yet there are many grasses in which it reaches a considerable
size. Zizania aquatica (fig. 22, PI. Ill) has a well-marked epiblast
extending from the base of the lengthened axis to about the middle of
the plumule, or even further.
In the genus Stipa there are marked differences in the size of the
epiblast in the different species. S. tenacissima (fig. 30, PI. IV) has a
very small one; in S. pennata it is long and attenuated ; while in S.
riehardsoni (fig. 36, PI. V) and 8. viridula (figs. 32 and 33, PI. IV) it is
very large and broad. Sometimes the margin of the epiblast is curved
or deeply keeled, although in the large majority it is straight. Homa-
locenchrus oryzoides (fig. 28, PI. IV) has a very large epiblast which
greatly resembles the form of the scutellum. It is large and broad at
the base and has a shield like appearance. A small .protuberance
occurs at the base similar to that in the scutellum.
A fact which seems to indicate that the epiblast has the same mor-
phological value as the scutellum is, that it is inserted on the axis
almost at the same height. Even in Zizania (fig. 22, PI. Ill), where the
axis elongates to a great length and the insertion of the scutellum is
almost at the base of the embryo, the epiblast is inserted directly
opposite.
The absence or presence of the epiblast appears to be fairly constant
in the different tribes, and the presence of an epiblast in a tribe where
the majority of the genera have none may indicate that it is not in its
natural position. The tribes Andropogonece and Maydew, to conclude
from the genera examined, might be regarded as being without an
epiblast. The scutellum almost entirely surrounds the embryo, as may
be observed in any of the cross sections figured, more especially among
the Maydece. In the tribe Zoysiece there occur genera without an
epiblast, as Nazia, Trachys, and Anthephora, while Zoysia has a dis-
tinct one. The. Tristeginew, to conclude from Bechera and Arundinella,
have no epiblasts. The Panicew appear to be without an epiblast, the
only exception being Olyra, which has a very large epiblast covering
the plumule.- From its great resemblance to the embryos of Leersia
and Oryza it seems probable that it should be placed with them, or
should form a separate intermediate tribe. The Oryzece appear to have
a very large epiblast. The Phalaridew, so far as examined, vary,
Anthoxanthum and Phalaris having small epiblasts, while Ehrharta
has none.
The Agrostidece examined, although varying greatly in their external
form, all possess an epiblast. In the large majority it is small, but in
17
some, as in Stipa, it is remarkably large, extending the whole length
of the plumule. The Avenece also, so far as examined, all possess an
epiblast. It is in the Chloridece that the most remarkable and varying
formations of the embryo are to be found. Meusine (fig. 52 A-D, PI.
VI) has a round nut-like fruit, with a small embryo having a very large
epiblast; while ISpartina (fig. 53, PI. VI) has a long fruit, with the
embryo extending almost the length of the seed, but with no trace of
an epiblast. Between these occur the genera Bulbilis (fig. 58, PI. VI),
Leptochloa (fig. 56, PI. VI), AstreMa (fig. 55, PI. VI), Cynodon (fig. 57,
PI. VI), and Beckmannia (fig. 60, PI. VI), each with an epiblast.
In the Festucece, a very large percentage of the genera have a well-
formed epiblast, but iu Bromus and some others it is absent. Among
the Hordece, Secale (fig. 67, PI. VII) and Hordeum (fig. 35, PI. IV) are
without an epiblast, while in Lolium (fig. 70, PI. VIII) and Triticum
(fig. 69, PI. VII) it is present. Flymus (fig. 72, PI. VIII) has a very
light projection at the point where the epiblast is usually situated, and
might be regarded as a transition stage between those with and those
without an epiblast.
Among the Bambusece only the genera Arundinaria (figs. 74, 75, 76,
PI. VIII) and Bambusa have been examined. They possess very large
broad epiblasts.
It appeais, therefore, in most cases that the tribes Maydece, Andro-
pogonece, Zoysiece, Tristeginece, and Panicece are without epiblasts, while
in the Oryzece, Phalaridece, Avenece, Chloridece, Hordece, Festucece, and
perhaps, the Bambusece, it is usually present.
The following table will show that it is not correct to regard the
epiblast as usually wanting in the Graminese.
MAYDE*.
Without epiblast.
With epiblast.
Encblaena.
Zea.
Coix.
Tripsacum.
ANDROPOGONE^S.
*Saccharum.'
Andropogon.
* SORGHUM.
*Erianthu8.
Apluda
ZOYS1E.E.
Perotis.
* Trachys.
Anthephora.
Zoysia.
Nazia.
'The genera starred (*) are taken from Bruns'a work, not examined by the writer.
20946— No. 19 2
18
RISTEGINEiE.
' Arundinella.
* Beckera.
PANICE/E.
Paspalum:
Pennisotum.
Chaetochloa.
*Panicum.
Tricholaena.
* Pennisetum.
*Berchtoldia (Chaetium).
Cenclirus.
ORYZE^E.
Oryza.
Zizania.
Homalocenclirus.
Lygeum.
Pharus. 2
phalaride^e.
•Ehrharta.
Phalaris.
Anthoxantkum.
Savastaua.
AGROSTIDKjE.
Stipn.
Phleum.
* Polypogon.
Sporobolns.
*Piptatherum.
Calaniagrostis.
Erioconia.
Oryzopsis.
Brachyelytrum.
Ammophila.
Milium.
Cbieturus.
* Apera.
Lagurns.
* Aristida.
Cinna.
AVENK*.
Avena.
Arrhenatherum.
Dauthonia.
Aira.
Holcus.
1 Van Tieghem. Ann. Sci. nat. Ser. 5, 15 : 240.
19
Spartina.
Secale.
Hordetun.
Asperella.
CHLORIDE^'.
Leptoohloa.
Eleusine.
Chloris.
Beckmannia.
Cynodon.
Astrebla.
Bulbilis.
* Nardus.
Lolium.
Triticum.
*Aegilops.
* Lepturus.
Elymus.
FESTUCACE^E.
* Eohinaria.
Cyno8urus.
Festuca.
Leptochloa.
Melica.
Koeleria.
Korycarpus.
Deamazeria.
Dactylis.
Poa.
Panicnlaria.
* Lamarkia.
* Avellinia.
Briza.
* Brachypodium.
Triodia.
BAMBUSE^;.
I Aiundiuaria.
I * BamTjusa.
THE PLUMULE-SHEATH.
This peculiar structure is found in all grasses, completely surround-
ing and protecting the plumule, with the exception of a small opening
or slit toward the apex on the side opposite to the scutellum. At ger-
mination the young leaves break through this sheath, which soon
afterwards dies down. The plumule-sheath always has two distinct
vascular bundles situated laterally and slightly inclined toward the
scutellum. Considerable controversy has arisen as to whether this
organ is a part of the cotyledon or whether it represents the first true
leaf of the embryo. This will be treated of later under the chapter on
the homology of the parts. It usually originates directly under the
plumule and close to the insertion of the scutellum, although it is
* Boissiera.
* Schismus.
Bromus.
Gynerium.
20
widely separated from the scutellum in many grasses. See Zizania and
Homalocenchrus (figs. 22 and 28, Pis. Ill and IV). Because of its thick-
ness, it is specially adapted for a protective organ.
THE ROOT SYSTEM.
The large majority of the embryos of grasses have only one radicle,
situated at the base of the embryo, usually in a vertical position, but
sometimes turned obliquely, as in Oryzopsis (fig. 38A, PI. V) and Stipa
richardsonii (fig. 36, PI. V), or, again, completely horizontal, as in
Eriocoma (fig. 34, PI. IV), Oryza sativa (fig. 27, PI. IV), and Eleusine
(fig. 52A-D, PI. VI). In Homalocenchrus oryzoides (fig. 28, PI. IV) it
has a slightly upward tendency.
There are, however, embryos with numerous lateral roots. Triticum
eestivum (fig. 69, PI. VII) has four lateral roots, two on each side of the
scutellum. Zizania (fig. 240-Q, PI. Ill) has three, situated directly
under the plumule, a long distance from the main radicle. Goix (fig. 1,
PI. I) has four radicles, obliquely one above the other on the axis. In
the illustration only three are seen, as they are not all in the same plane.
Hordeum vulgare (figs. 65, 66, Gr and H, PI. VII) has eight secondary
radicles, three on each side of the scutellum and two in front. On
germination the primary radicle is soon outstripped in growth by the
secondary ones. Both the primary and secondary ones are surrounded
by a compact mass of cells which form the coleorhiza or root-sheath.
Each radicle terminates in a rootcap, the cells of which appear as
regular continuations of the rows of cells iu the radicle. The rootcap
can thus be distinguished from the coleorhiza, in which the cells are
very irregular. The rootcap is not connected with the coleorhiza. The
former is produced from the embryonic tissue, while the latter is derived
from the preembryonic tissue and is connected with the lower part of
the scutellum. In dissecting out the embryo the radicle or radicles,
with their rootcaps, easily separate from the coleorhiza, leaving the
latter at the base of the sockets in the lower part of the scutellum.
LATERAL BUDS.
In a number of genera of the tribe Hordes there is a lateral bud in
the axil of the plumule-sheath : Hordeum (fig. 65, PI. VII), Triticum (fig.
69, PI. VII), Elymus (fig. 72, PI. VIII), and Secale (fig. 67, PI. VII).
Bruns regards this as proving that the plumule-sheath must represent
a leaf. Similar buds, however, may be found in Polygonum, Eumex,
and a large number of plants with axillary stipules. Van Tieghem
describes and figures lateral buds in Avena sativa, but it was not pos-
sible, after making many paraffin sections through different embryos, to
discover them. This circumstance is remarkable in that Avena belongs
to the tribe Avenece, while all other genera in which lateral buds have
been found belong to the tribe Hordece. Bruns, however, figures and
describes a Bambusa with a large lateral bud in the axil of the plumule-
sheath.
21
THE FIBRO-VASCULAR SYSTEM.
The fibro-vascular system of the embryos of the Oraminece may be
considered under three main divisions, according to the manner and
place of insertion of the plumule-sheath on the axis and its connection
* with the scutellum.
1. The plumule-sheath is inserted on the axis directly above the
insertion of the scutellum : Stipa (fig. 36, PL V), Phleum (fig. 41, PI. V),
Ammophila (Fig. 42, PL V), and perhaps all of the Agrostidew.
An example of this modification occurs in Stipa viridula (figs. 32 and
33, PL IV). Avascular bundle passes through the entire length of
the scutellum. At the insertion of this bundle ou the axis two branches
are sent off from it which traverse the plumule-sheath (fig. 33, PL IV),
while the main branch continues into the axis and then descends to the
radicle. A little above this insertion numerous small bundles form and
run up into the young leaves and vegetation point. As these different
bundles are not all in the same plane, it is not possible to obtain a sin-
gle section showing them. In any transverse section of the plumule,
however, the bundles of the plumule-sheath may be seen quite dis-
tinctly.
In Eriocoma cuspidata (fig. 34, PL IV) the bundles ascend from the
axis into the plumule-sheath, while in a cross section of Stipa richard-
soni (fig. 37B, PL V), taken below the insertion of the scutellum on the
axis, the vascular bundle may be seen entering the radicle. Again, in
Tritieum (fig. 69, PL VII) a bundle may be seen entering the first true
leaf. Hordeum (fig. 65, PL VII) shows the bundles passing up iuto the
second true leaf and the vegetation point, while several may be seen
branching off from the axis into the secondary radicles. All the genera
of the tribes Agrostidew and Hordece, so far as examined, have this
arrangement of their vascular systems.
2. The plumule-sheath is inserted on the axis at some distance from
that of the scutellum, with which it is connected by a vascular bundle
traversing the axis: Zizania (fig. 22, PL III) and Homalocenchrus (fig.
28, PL IV). The embryo of Zizania aquatica (figs. 22, 23 A and B, 24
A-T, PL III) has a remarkably long axis, which separates the insertion
of the plumule-sheath and the scutellum to a very considerable degree.
It will be noticed in the longitudinal section (fig. 22, PL III) that two
vascular bundles traverse the axis, one terminating in the main radicle,
while the other curves sharply round and traverses the long linear
scutellum. The exceedingly large epiblast is devoid of any vascular
system. In the transverse sections (fig. 24 A-T, PL HI) it is found that
in A, a section taken through the apex of the plumule-sheath, the two
bundles have joined into one. In B they are beginning to separate,
while in O and D they are entirely free. Figure E shows a section
through the tip of the first leaf of the plumule, the plumule-sheath with
its two widely separated lateral bundles surrounding it. Figures F-L
illustrate sections taken through the plumule at different heights, show-
ing the arrangement of the leaves with their bundles. The bundle in
22
the center of the leaf is always a little larger than the lateral ones.
The bundle of the scutellum now appears distinctly in all sections
taken through the regiou of the plumule. ST represents a section taken
directly underneath the plumule- sheath. The bundles of the sheath
have united with those of the' leaves and appear very irregular, with a
secondary radicle appearing on each side. A little lower dowu a third
secondary radicle is seen on the side of the axis next to the scutellum.
The axis now for a considerable distance presents the appearance shown
in P and Q, with two distinct, separate, vascular bundles in the center.
At the base of the long axis one of these bundles situated nearest to
the scutellum joins with the bundle of the latter, as in S, while the
other continues down into the main radicle, as in T. This seems to
prove conclusively that the plumule sheath is not an independent leaf,
but that it belongs to the scutellum.
There is no difference between this group and the first, represented
by the Agrostidece, except that between the insertion of the plumule-
sheath and the scutellum there occurs a very loug axis representing
the first node.
3. The plumule-sheath is inserted on the axis at the base of the plu-
mule, but its fibro-vascular bundles are not directly connected with
that of the scutellum: Zea, Coix, Pennisetum, Paspalum, Panieam,and
Spartinct. Zea mays may be taken as typical of this arrangement of
the vascular system, as shown by a series of sections from the radicle
to the plumule (figs. 3, and 4 A-P, PI. I). Fig. 4 A represents a cross
section through the main, radicle. There are two systems of vessels,
consisting of six large ones toward the center and about sixteen smaller
ones on the outside, which, along with their conjunctive tissue, make
up the central cylinder. Section B, taken somewhat higher up, above
the region of coleorhiza shows the axis with its bundles beginning to
form round the periphery of the central cylinder, the two systems of
vessels remaining the same as in the radicle. The dark portions of the
scutellum are sections through the lateral branches of the scutellum
♦bundle. These peripheral bundles widen and come closer and closer
to the center until they reach the condition figured in C, where there
is an irregular mass of vascular strands and bundles with only a few
of the vessels. Immediately above this the bundles arrange them-
selves round the periphery, leaving only a few in the center, while a
vascular strand branches off and penetrates through the cortical
parenchyma into the scutellum, where it divides into an ascending and
descending branch, as in D. The large vessels have returned to their
original. position, while the smaller ones have become fewer, and are
arranged irregularly nearer the center. At E, a section taken through
the upper part of the scutellum, two radicles emerge from the axis to
the right. Vascular bundles are found both in the periphery and in
the center of the cylinder. The axis now continues in a regular form
with its two systems of vessels and bundles arranged in the periphery,
23
until just below the plumule, where several bundles in the periphery-
unite on either side and branch off into the plumule-sheath. Soon
numerous, bundles form in the center, until the whole axis is completely
filled with them. These arrange themselves in a definite manner and
run up into the leaves of the plumule.
There is no direct connection between the vascular bundle of the
scutelluin and those of the plumule-sheath, both originating from the
peripheral bundles of the axis separately. The same condition occurs
in all the genera of the Maydece, Chloridece, Panicece, and Andropogo-
nece examined, with slight modifications as to the number and size of
the vessels and bundles. This would seem to indicate that these tribes
are closely related to one another, although it is not exactly in accord-
ance with Hackel's classification of the tribes with reference to the
Chloridew.
HOMOLOGY OF THE PARTS OP THE EMBRYO.
To what do the scutellum, epiblast, and plumule-sheath correspond;
from what have they been developed ; and to what parts of the leaf and
spikelet of the grasses are they homologous ?
The scutellum is at present generally r egarded as the cotyledon, cor-
responding to the single cotyledon characteristic of the group of
monocotyledons, but differing from them in not emerging from the
caryopsis at germination.
The epiblast has been regarded in various ways by different authors.
Bernhardi, Schleiden, Schacht, and, later, Van Tieghem, regard the
epiblast as part of the cotyledon. Haustein concludes that it is merely
an insignificant tf ichomatic projection of the hypocotyl. The majority
of writers, however, with Poiteau, Mirbel, and Bruns, regard it as a
second rudimentary cotyledon, and in embryos in which it is wanting,
look upon it as having become completely aborted.
Van Tieghem 1 in his new classification of the phanerogams based
upon the ovule, revised his opinion concerning the epiblast, regarding
it as a second rudimentary cotyledon, and explaining its partial or
complete abortion as due to the pressure more or, less exerted by the
seed coat or pericarp upon the embryo. From this and other char-
acters of the integuments and ovules he is led to believe that the
Graminece are in reality dicotyledons, which have accidentally become
monocotyledons.
In spite of the fact that there has never been found the slightest
trace of a vascular system in the epiblast, yet it seems most reasonable
to regard it as a second rudimentary cotyledon. One inclines to this
view from the study of the perfectly developed epiblasts of Homalocen-
citrus, Zizania, and Oryza, where they are inserted on the axis opposite
the insertion of the scutellum.
1 Comptes Rendu s seanc. l'acad. des Sciences, 124 : 1896-97.
24
The pluinule-sheath is, of all the organs of the embryo, the most
striking and difficult to explain. Three very different theories are
held regarding its interpretation. To the first we attach the names of
Hofmeister and Sachs, who regard it as an outgrowth of the so-called
hypocotyledonary internode.
The adherents of the second view regard it as an independent leaf
belonging to the plumule and next in leaf arrangement to the scutel-
lum. According to this the plumule-sheath, which is directly above
the scutellum on the same side of the axis, would not correspond to the
distichous arrangement of grass leaves; but if one regards the epiblast
as a leaf, i. e., a second cotyledon, then the apparent disagreement is
explained and the plumule- sheath becomes the third leaf alternating
with the epiblast. Bruus, who is a strong advocate of this view, sees
no reason why Hanstein should deny the independent nature of the
plumule- sheath because of its origin.
Let us briefly follow the, development of Braohypodium according to
Hanstein's investigations. The young embryo is at first a spherical
mass composed of three with sometimes a fourth smaller cell. These
cells divide several times in all directions and the embryo takes on a
club-shaped form, becoming longer and narrower at the base. This
many-celled body is at this time without distinct internal or external
differentiation. The lower-most cell, which has now become considera-
bly divided, later goes to form the suspensor, while the two upper cells
form the embryo proper. Soon the internal differentiation of the
radicle can be seen with its dermatogen, periblem, and pleroine. The
second stage of development takes place in the external part of the
embryo. In the wall there occurs a depression whieh marks the divi-
sion of the scutellum from the hypocotyledonary part. The tissue
immediately above this depression is the cotyledon, from which a part
of tbe plumule-sheath soon emerges, while that on the lower side forms
the vegetation point with its later-developed leaves. Tbe projection on
the upper part of the embryo, i. e., on the upper side of the depression,
shows again on its upper surface another depression similar to the first,
thus forming a second projection. At the same time a projection in the
form of a half collar has formed on the lower part below the vegetation
point. These two projections stand opposite one another like lips.
Finally they grow and their margins unite to form a complete cap over
the plumule. Tbe occurrence of a slit in the mature plumule- sheath is
in all probability caused by the incomplete junction of the margins of
these collar-shaped projections. Tbe tissue above this second depres-
sion, which sometimes curves down to a considerable degree pro-
tecting the plumule, forms that part of the cotyledon known as the
cotyledonary-sheath. Thus the origin of the plumule sheath indicates
that it must be a part of the scutellum. To regard the plumule-sheath
as an independent leaf as Bruus has done, one must look upon it as
arising from a stem and not from a primordial leaf, which, according to
Hanstein's investigations, is evidently the case.
25
The third view is that the plumule-sheath is a ligule-like growth pro-
ceeding from the scutellum as an inseparable part. The existence of
an intermediate part between the insertion of the plumule- sheath and
that of the scutellum in many embryos, is relied upon by Bernhardi,
Bruns aud others as positive proof that there can be no connection
between these organs. By many authors it has been called an inter-
node, which latter always develops between two leaves and not between
two parts of a leaf.
Bruns says that while in Uuchlwna the two insertion points are near
together, it hardly seems plausible in the case of Spartina, and espe-
cially of Zizania, to regard two organs which are so widely separated
from one another as the same. The occurrence of a bud in the axil of
the plumule-sheath also influences his conclusion that the plumule-
sheath must represent a leaf.
From a careful study of the vascular system of the different tribes,
together with Hanstein's investigations, one is led to believe with Van
Tieghem and Celakovsky that the so-called internode between the
plumule-sheath and the scutellum, occurring so distinctly in Zizania
and Homaloceuchrus, and not at all in the genera of the Agrostidece,
is nothing but the first unusually lengthened node. The ligule-like
growth, the plumule- sheath, is usually inserted directly over the scutel-
lum and the plumule-sheath in the mature fruits of Zizania, Homalo-
ceuchrus, and the Chloridece, or as in Oryza (according to Bruns and
Schlickum) soon after germination.
The vegetative leaf of the grasses is composed of a sheath and
blade and a more or less strongly developed ligule inserted at the
point of junction of the sheath and blade. The ligule is usually small,
without chlorophyll and stomata, and exclusively parenchymatous,
but as Duval-Jouve 1 has shown in Ammophila arenaria, it attains a
length of about 4 centimeters and possesses nerves with chlorophyll
and stomata. The ligule thus represents a double sheathing axillary
stipule.
Of the three parts of the leaf it is the sheath which develops last,
by an intercalary growth, which raises up the blade and ligule.
Comparing the culm leaf with the scutellum and plumule-sheath, the
cotyledonary leaf of the embryo, one finds that the latter has no
sheath. Its sessile blade, however, elongates to form the scutellum,
while the pumule-sheath, which is homologous with the ligule, attains
a great size with vascular bundles similar to the ligule of Ammophila
arenaria. It is provided with two prominent lateral nerves, which
later acquire chlorophyll and stomata.
The homology of the parts may in the same manner be carried out in
the spikelet. The awn of the floral glume, when present, is regarded
as corresponding to the blade of the leaf, and therefore to the scutel-
lum of the embryo. When the awn is inserted on the back of the
1 Anatomie de l'arete des Graminees Mem. de l'ao. des Sci. et lettres.
1871.
Montpellier.
26
glume some distance from the apex, that part between the insertion
and the apex is regarded as corresponding to the ligule, and, in conse-
quence, to the plumule- si) eath. That part of the glume below the
insertion of the awn is regarded as the sheath of the leaf, while its
analogous structure in the embryo has been arrested in its development.
Colomb, 1 who has investigated the stipules of many plants, also takes
up the ligule and sees in it an analogy to the stipules of Potamogeton
and Smilax. Celakovsky 2 makes a comparison between these, adding
another plant, Ficus elastica. He carries his homology still further to
the mosses, believing that the moss capsule is homologous to the
cotyledon and the seta or their bases to the hypocotyl.
DETAILED DESCRIPTIONS OP FRUITS.
Tribe Mayde^.
The fruits of the genera of this tribe are large, ellipsoidal or round-
ish, and inclosed, with the exception of Zea, in a hard capsule formed
of the glumes or of part of the articulate rachis. They have a very
large embryo, with the scutellum almost completely surrounding the
plumule.
Goix lachrynue-jobi L. (figs. 1, 2 A-G, PI. I). The structure of the
embryo of Goix resembles that of Zea mays, the main difference con-
sisting in the former possessing four lateral radicles. Only three are
shown in fig. 1, the fourth and uppermost one not being in the same
plane. Fig. 2 A represents a transverse section through the upper
part of the plumule, showing the plumule- sheath with its two bundles
and the first and second true leaves in their normal position. A sec-
tion through the base of the plumule (fig. 2 B) shows the plumule-
sheath and a small part of the first, true leaf. Within is the axis with
its numerous bundles which belong to the leaves of the plumule.
At 0 is the axis, with its numerous bundles and the plumule- sheath.
Some of the bundles in the periphery of the central cylinder unite and
branch off into the plumule- sheath on each side. A little lower down,
between the insertion of the plumule- sheath and that of the scutellum
the axis appears with its numerous bundles arranged in the periphery
of the central cylinder (fig. 2 D). Fig. 2 B shows the scutellum
inserted on the axis by its broad, fibrovascular bundle, at the same
time cutting through the first lateral radicle on the opposite side. A
number of ducts are scattered here and there in the axis. The axis
terminates in the lowermost radicle, the central cylinder having six
distinct ducts or vessels. Fig. 2 F shows a section through the upper
part of the lowermost radicle and one of the lateral radicles, while G
represents a section through the lowermost radicle. Each radicle is
provided with a root-cap while the coleorhiza surrounds them all. The
1 Kecherches sur les stipules. Ann. des Sci. nat. Ser. 6, 1 : 19. 1887.
2 Ueber die Homologien des Grasembryo. Bot. Zeit., Sept., 1897.
27
scutellum entirely surrounds the remainder of the embryo, as may be
seen in cross section or in the longitudinal section (fig. 1). There does
not appear to be such a direct connection between the vascular bundle
of the scutellum and those of the plumule-sheath, as in Zizania (fig. 22,
PI. Ill), Somalocenchrus (fig. 28, PI. IV), and other embryos. The vas-
cular bundle of the scutellum, as in the other genera of the Maydew,
branches into two, one traversing the upper and the other the lower
part of the scutellum, and these again sending off lateral branches.
The leaves of the plumule are arranged as in all grass embryos.
Zea mays L. (figs. 3, 4 A-F, PI. I). — The vascular system of Zea has
already been described. The general structure of the embryo differs
but little from that of Coix. Instead of four large lateral radicles it
has one large main radicle (fig. 4 A) and two smaller secondary ones at
the insertion of the scutellum bundle on the axis. The scutellum sur-
rounds the remainder of the embryo like a mantle, the margins almost
coming together, but separated by a long, narrow groove (figs. D and
E). There is a deep cleft between the base of the scutellum and the
coleorhiza (fig. 3).
Trip8acum dactyloides L. (figs. 5, 6, 7, A-B, PI. I). — The embryo of
Tripsacum is very similar to that of Zea and Goix, except that it has
only one radicle. The axis is remarkably long and consists of a num-
ber of vascular bundles, as in Voix. About halfway down the axis the
bundles in the periphery increase toward the center, presenting the
same condition as in Coix and Zea, again returning to the periphery
and disappearing as they approach the radicle. The insertion of the
scutellum-bundle is not as in Goix, Zea, and Euchlcena at some distance
from the plumule but directly under it, where the plumule-sheath also
branches off (fig. 6). The scutellum-bundle soon after leaving the axis
divides, one branch traversing the lower, and the other the upper part
of the scutellum, while these in turn have lateral branches (fig. 6).
Aside from these bundles connected with the vascular system there are
conducting vessels running irregularly through the scutellum, appar-
ently nourishing organs for the plumule and radicle, as they can be
traced to be directly connected through the epithelial layer with the
other parts of the embryo (fig. 6).
Euchlcena mexicana Schrad. (fig. 8, PL II). — The structure of the
embryo of Euchlwna is almost identical with that of Zea mays, except
that it has no secondary radicles and the insertion of the scutellum-
bundle is at some distance from the plumule.
• Tribe Andropogone^e.
The fruits of the tribe Andropogonem have an embryo which is usually
about half the size of the fruit itself. As in the Maydece, the scutellum
almost completely surrounds the remainder of the embryo. By com-
paring the embryo of Andropogon (fig. 9, PI. II) with Zea (fig. 3, PI. 1)
one notices a striking similarity. The scutellum-bundle is inserted on
28
the axis at some distance from the plumule, as in the majority of the
Maydew.
Andropogon saceharatus i (fig. 9, 10, A-C PI. II). — The scutellum almost
surrounds the plumule. The projection appearing in fig. 9 like an epi-
blast is only a longitudinal section through one of the margins of the
scutellum. The scutellum -bun die is inserted on the axis at some dis-
tance from the plumule, while directly under the plumule two bundles
branch off into the plumule-sheath. Fig. 10 A shows a section through
the plumule with its plumule-sheath and bundles of the first true leaf,
while fig. 10 B represents a section taken through the axis between the
plumule and the insertion of the scutellum bundle. Only one radicle
is present with a large vessel in the center and five smaller ones
around it in the central cylinder (fig. 10 C). There is a deep groove
between the scutellum and the coleorhiza.
Apluda cristata (figs. 11, 12, PI. II). — The embryo of Apluda cristata
resembles those of the Maydew and Ghloridece. There is no epiblast.
The radicle appears as in fig. 12, with one large vessel and six smaller
ones in the central cylinder. This arrangement continues through the
axis until near the insertion of the scutellum, where vascular bundles
appear. These continue through the lengthened node as far as the
base of the plumule, where they send off branches into the plumule-
sheath. The ring around the radicle in fig. 12 represents a cross section
through the coleorhiza.
Tribe Zoysie^s.
The Zoysiece resemble on the one hand the Andropogonew, through
Trachys, Anthephora (fig. 13 A-E, 1 PI. II), and Perotis (fig. 15 A-D),
and on the other hand Oryzece through Zoysia (fig. 14 A-D) and Nazia.
Bruns, in a list of genera, represents Nazia without an epiblast, while
in his figures he represents it with an epiblast, both in longitudinal and
transverse sections. The scutellum in Anthephora and Perotis is
inserted at some distance from the plumule, while in Zoysia it is
inserted directly under it. The radicle of Zoysia is also curved in a
horizontal direction like Oryza.
Tribe Tbistegine^:.
Unfortunately no representatives of this tribe could be secured.
Bruns, however, who has investigated the fruits of Beckera and Arun-
dinella, found them to be without an epiblast, and similar to the
Zoysiece.
Tribe Panice^e.
The general appearance of the fruits of the Pamieew is similar to
those of Andropogonece. They are, with one exception, without an epi-
blast, and have the scutellum-bundle inserted at some distance from
the plumule. Olyra is the only genus which has an epiblast. It is
29
described and figured by Bruns, and differs in every respect from the
other Panicece. The scutellum is broader than long, while the plumule
is covered by a very large epiblast. A peculiarity mentioned by Bruns
is that the radicle is hollowed oat. Owing to the general appearance
of the fruit and embryo, with its large epiblast and the insertion of the
scutellum-bundle, also the fact that the flower is monoecious, would seem
to indicate that it does not belong to the Panicece. It might, perhaps,
be placed with the Oryzece or form an intermediate tribe with Zoysia
between the Panicece and Oryzece.
Pennisetum spicatum (figs. 16, 17, 18, PL II). — The fruit of Pennisetum
has a very large embryo. The scutellum surrounds the remainder of
the embryo, although not to such an extent as in the Andropogonece
and Maydece. The projection opposite the scutellum in fig. 16 is not
an epiblast, but a longitudinal section through the margin of the scu-
tellum. A single large radicle is present, which consists of one large
vessel in the center and six small Ones surrounding it in the central
cylinder (fig. 18). The ring around the radicle represents the coleorhiza
with its attachment to the scutellum. Fig. 17 represents a cross section
through the plumule, showing the scutellum with its bundle and the
plumule-sheath with its two lateral bundles. Within is the first true
leaf. The scutellum-bundle is inserted on the axis at some distance
from the plumule (fig. 18).
Ghcetochloa macroehceta (fig. 19, PL III).— The embryo of this nut-like
fruit resembles in the main other Panicece. The insertion of the
scutellum-bundle is, however, somewhat closer to the plumule. A deep
cleft or groove is present between the scutellum and coleorhiza.
Paspalum pubiflorum glabrum (figs. 20, 21, PL III). — The embryo of
Paspalum resembles that of Pennisetum, although, much smaller. It
possesses a large radicle, and its scutellum-bundle is inserted at some
distance from the plumule.
Tribe Oeyze^;.
To this tribe belong, among others, the genera Momalocenchrus,
Zizania, and Oryza. Great variation occurs in the size and formation
of the fruits. The embryo is usually small compared with the amount
of endosperm, but in Zizania it attains a considerable size. All the
genera belonging to this tribe have a well-marked epiblast.
Zizania aquatica (figs. 22, 23 A-B, 24 A-T, PL III) (see p. 21).— The
fruit of Zizania is long and linear, with an epiblast which reaches three-
quarters the length of the whole fruit. Figs 23 A and B show the rela-
tive size of embryo and endosperm ; A through the plumule, and B
through the axis or lengthened node. Figs. 24 A-T represent a series
of sections through the embryo from the apex of the plumule-sheath
to the main radicle. A and B show the two vascular bundles of the
plumule-sheath, which at this point are united into one. At 0 and D
they have become separated, while at E the plumule-sheath appears as
30
a complete ring, inclosing the upper part of the first leaf. The opening
in the plumule-sheath on the side opposite to the scutellum now appears
for a short distance as shown at G. At H, I, and J it is again closed,
and within is seen the arrangement of the leaves of the plumule. K
shows the first appearance of the epiblast, while at M it has increased
in size. Within the plumule-sheath and first leaf one sees the axis
with its bundles which belong to the remaining leaves of the plumule.
Immediately below the plumule are three secondary radicles repre-
sented in IN and O. The embryo for a considerable distance presents a
form similar to that shown at P. The vascular system in the region
of the secondary radicles presents a confused mass, but here it consists
of two regular strands which course the lengthened node. As they
approach the insertion of the scutellum the inner one becomes larger
until it unites with the bundle of the scutellum. E shows the attach-
ment of the epiblast to the axis, the division being marked by a dotted
line, while T is a section through the main radicle surrounded by its
coleorhiza.
Homalocenchrus oryzoides (fig. 28, PI. IV). — The fruits of Momalocen-
ehrus, although much smaller and of a different form from that of
Zizania, yet in the main possess the same structural characters of the
embryo.
Lygeum spartum (figs. 25, 26 A-E, PI. IV). — The embryo of Lygeum
differs from the other genera of the Oryzece examined in having a very
small epiblast. The insertion of the scutellum- bundle occurs directly
beneath the plumule. Also at this point branches are sent off into the
plumule-sheath (fig. 26 B). The radicle is here lengthened out to a
considerable extent. Lateral roots also arise from the node, as in fig.
26 O and D. Fig. 26 E shows a section through the main radicle, while
26 O shows parts of the secondary radicles and the base of the epiblast.
Oryza sativa (fig. 27, PI. IV). — Compared with the amount of endo-
sperm, Oryza has a very small embryo. The epiblast is large and
broad at the base. As in Lygeum, the insertion of the scutellum is at
the base of the plumule. The large radicle is directed obliquely
outward.
Tribe Piialaride^;.
Of the Phalaridece only Phalaris and Anthoxanthum (fig. 29, PI. IV)
were examined. These much resemble the Agrostidece, having a small
epiblast and a straight radicle. The scutellum-bundle is inserted at
the base of the plumule-sheath.
Tribe Ag-rostideje.
The Agrostidece may be characterized as fruits with small embryos,
always with an epiblast, which, however, varies greatly in size. The
scutellum-bundle is inserted on the axis at the base of the plumule.
Here it branches to the right and left, running up into the plumule-
31
sheath. The short axis terminates in a single radicle. Among the
peculiarities noticed in this tribe is the genus Stipa. Stipa pennata has
a well-marked epiblast more than half the length of the plumule, while
8. tenacissima (figs. 30 and 31, PI. IV) has a very small epiblast. In
fig. 31 the opening of the plumule-sheath is apparent. In 8tipa richard-
soni (figs. 3G and 37 A and B, PI. V) the epiblast extends more than
half the length of the plumule, and the radicle is directed obliquely
outward. Although 8. viridula (figs. 32 aud 33, PI. IV) has a very
small fruit, yet its embryo has proportionately the largest epiblast.
Eriocoma cuspidata (figs. 31 and 35, PI. IV). — The fruit of Eriocoma
resembles that of Oryzopsis, but has a very large epiblast which extends
the whole length of the plumule. The scutellum differs from Oryzopsis
in having a groove at its base. This character, together with the long,
densely hairy, flowering glumes, would warrant its being placed as a
separate genus Eriocoma, which is regarded as a subgenus by Hackel.
Oryzopsis micrantha (figs. 38 A and B, PI. V), Phleum pratense (fig.
41, PI. V), Oinna arundinacea (figs. 39 and 40, PI. V), and Brachyely-
trum erectum (fig. 43, PI. V) all have a well-marked epiblast. The last
named can easily be recognized by a long, pointed projection proceeding
from the pericarp. This projection contains no starch, and its presence
is remarkable from the fact that it is the only fruit in which such a
structure has been found. Ammophila arenaria (fig. 42, PI. V) presents
a peculiar appearance. Its cotyledonary sheath extends down to the
apex of the plumule. The scutellum also branches into three in the
upper part.
Tribe Avbne^;.
The Avenece resemble the Hordece in the structure of fruits. The
embryo is usually small compared with the amount of endosperm.
Lateral roots occur in Avena. The scutellum-bundle is inserted at the
base of the plumule and continues down into the axis in the form of a
loop.
Avena safiva (figs. 44, 45, 46 A-B, 47 A-G, 48, Pis. V and VI).— Fig.
47 A-G, Pi. V, represents a series of transverse sections through the
embryo from the plumule to the radicles. At A one sees the peculiar
shape of the scutellum, with its vascular bundle, while within is the
plumule-sheath, with its bundles, inclosing the first true leaf. B repre-
sents a section taken somewhat lower down in the plumule and shows
the position of the second leaf directly opposed to the first. The scu-
tellum-bundle branches at the base of the plumule, as may be seen at
0, to form the bundles of the plumule-sheath. Part of the plumule-
sheath is still present, while within is the axis with the first leaf and
its bundles just beginning to differentiate. Figs. D, E, and F show
the axis, and the epiblast which becomes larger toward the base. At
E only one radicle is present while at F there are three. G shows the
position of the four radicles. The main radicle is in the center with
one on each side to the right and left, and a fourth smaller one in front.
32
A longitudinal section of this small radicle may be seen in fig. 48,
PL VI. The scutellum-bundle forms a loop in .the axis as in fig. 48, a
strand branching off from it forms the central bundle of the first true
leaf. Fig. 45, PL V, represents a section facing the embryo. The main
radicle with its two lateral radicles to the right and left are all sur-
rounded by a coleorhiza. Pigs. 44 and 46 A and B, PL V, represent
longitudinal and transverse sections through the whole fruit showing
the relative size of endosperm to embryo.
Holcus lanatus (fig. 51, PL VI.), Arrhenatherum elatias (fig. 49), and
Danthonia spicata (fig. 50) all have a small epiblast and a single termi-
nal radicle with the scutellum-bundle inserted directly under the
plumule.
Tribe Chloride
The Ohloridece, according to the characters of their embryos, are
more closely allied to the Andropogonece than to the Avenece and Festu-
cew, with which they are placedin Hackel's classification. The fruit varies
considerably both in regard to its form and the structure of the embryo.
There is a spherical nut-like fruit, as in Eleusine (fig. 52 A-D, PL VI),
with a well-marked epiblast, and a long linear fruit with an embryo
more than half the size of the fruit itself and without an epiblast, as in
Spartina gracilis (fig. 53). The scutellum is inserted on the axis at
some distance from the plumule.
Eleusine coracana (fig. 52 A-D, PL VI). — This peculiar nut-like fruit
has an embryo with a very large epiblast. The radicle is in a hori-
zontal direction, while a deep groove is present between the scutellum
and coleorhiza. The insertion of the scutellum-bundle is close to the
base of the plumule, while the axis between the plumule and radicle is
very short. Pig. 52 A represents a longitudinal section through the
embryo, while at B we see the plumule with the large epiblast pro-
tecting it.
Spartina gracilis figs. 55, 54 A-O, PL VI). — In contrast to Eleusine
it has a long linear fruit with an embryo reaching almost its whole
length. The general appearance of the embryo reminds one of Zizania
aquatica, as the insertion of the scutellum is a considerable distance
from the plumule-sheath. One single vascular strand courses the length-
ened node until it sends off a branch to the scutellum, and then con-
tinues down into the very small radicle. Fig. 54 A, B, C show sections
through the radicle, lengthened node, and plumule, respectively. It is a
noteworthy fact that this is the only genus of the Ghloridew examined
which does not have an epiblast.
Astrebla pectinata (fig. 55, PL VI). — The embryo of Astrebla is very
large, with a very small epiblast. A deep groove is present between
the scutellum and the coleorhiza. The scutellum-bundle is inserted on
the axis at some distance from the plumule. The axis terminates in
a single radicle, which preserves its root structure until just before it
reaches the insertion of the scutellum, where vascular bundles appear.
33
Beckmannia erucwformig (fig. 60, PI. VI), Bulbilis daetyloides (figs. 58
and 59, PL VI), and Leptochloa imbricata (fig. 50, PI. VI) have about
the same characteristics.
Tribe Festuceje.
The embryo of the Festucece is usually small. There is, according
to Bruns, great variation in the presence and ab.sence of an epiblast
in this tribe.
TJniola latifolia (fig. 61, PI. VII). — A broad epiblast reaches about
half the length of the plumule. The scutellum-bundle is inserted on
the axis at some distance from the plumule, while the single radicle is
turned obliquely outwards.
Desmazeria sicula (fig. 63, PI. VII), Gynosurus cristatus (fig. 04), and
Panicularia aquatica (fig. 62, PI. VII) all have the epiblast well marked.
The scutellum-bundle differs from that of TJniola in being inserted
directly at the base of the plumule. The axis terminates in a single
radicle.
Tribe Hobde^e.
The tribe Hordece may be characterized as having large fruits. The
embryo usually has several radicles and a lateral bud in the axil of the
plumule-sheath. A transition seems to take place between those with-
out an epiblast, as in Hordeum (fig. 65, PI. VII), and those with a dis-
tinctly formed epiblast as in Triticum (fig. 69, PI. VII).
Hordeum vulgare (fig. 65, 66 A-H, PI. VII). The fruit of Hordeum
vulgare has many peculiarities not found in other grasses. There are
two, and in some parts three, layers of gluten cells, while in nearly all
grass fruits there is only one. This embryo often has, besides its main
radicle, eight secondary ones, three on each side of the scutellum and
two in front. In the axil of the plumule-sheath next the scutellum
there is a large lateral bud (see p. 20). By examining figs. A-F it will
be seen that the scutellum-bundle is composed of two strands which
unite just before their insertion on the axis. The scutellum is inserted
on the axis at the base of the plumule, a secondary radicle also emerg-
ing from it at this point, thus making the axis very short. At fig. 65
the bundles may be seen which belong to the first aud second leaves
and the vegetation point. Those of the plumule-sheath not being in
the same plane are not represented. A transverse section through the
upper part of the plumule (fig. 66) shows the opening in the sheath
opposite to the scutellum and the two bundles situated laterally.
Within is the upper part of the first true leaf. The scutellum shows
a peculiar groove on its convex side next to the endosperm (fig. 66, A, B).
B shows a similar condition a little lower down through the plumule.
AtO and D the position of the first leaf opposite to the plumule- sheath,
the second opposite the first, and the third opposite the second, accord-
ing to the true distichous arrangement of all grass leaves may be noted.
20946— No. 19 3
34
E shows a section taken at the base of the plumule with the bundles in
the axis which belong to the leaves of the plumule, also the two bun-
dles of the disappearing plumule-sheath. At F the scutellum bundles
are inserted on the axis. On the opposite side are two secondary rad-
icles in the center of the bundles of the axis, while to the right and left
appear the origin of the bundles of the plumule- sheath. At 0 the
scutellum-bundles are no longer present, while three secondary radicles
emerge from the axis. Four of the secondary radicles may be seen at
H with the axis continuing down to form the main radicle. These rad-
icles are all provided with a root-cap and surrounded by the coleorhiza.
Although no epiblast is found here yet there is a slight prominence
which might indicate its abortion.
Secale montanum (figs. 67, 68 A and B, PI. VII). — The structure of
the fruit of Secale resembles that of Hordeum vulgare. There is how-
ever only one secondary radicle. Not even a trace of an epiblast can
be seen. The coleorhiza surrounds both radicles, forming a deep groove
between them. At the base of the plumule-sheath next to the scutel-
lum there is a lateral bud. The scutellum-bundle consists of a single
strand, which is inserted on the axis almost directly at the base of the
plumule. At this poiat branches are sent off into the plumule-sheath.
The bundles in the axis belong to the leaves of the plumule while the
axis continues down into the main radicle, a branch being sent off to
the secondary radicle. Fig. 68 B represents a transverse section
through the upper part of the plumule and A through the main and
secondary radicles.
Elymu8 virginicus (figs. 72 and 73, PI. VIII). — The fruit of Elymus
has a very small embryo at the base of a long fruit. Although the
epiblast is not present yet there is a slight elevation which might be
regarded as a remnant of it. The scutellum bundle consists of a single
strand which curves around to the base of the plumule where it
divides into three branches, two of them going into the plumule-sheath
and the other continuing down into the axis and single radicle. A
lateral bud is present in the axil of the plumule-sheath. Fig. 73 rep-
resents a transverse section through the upper part of the plumule.
Loliurn rigidum (figs. 70, 71 A-C, PI. VIII). — The embryo of Lolium
resembles Secale montanum with only one large radicle. A lateral bud
is present in the axil of the plumule-sheath.
Triticum cestivum (fig. 69, PI. VII). — The fruit of Triticum wstivum
has been so frequently described by previous writers that it is not
necessary to treat it at length here. An excellent treatise by Bessey is
to be found in Bull. 32 of the Nebraska Agr. Exp. Station, 1894. Its
embryo has a small epiblast, a main radicle, and two secondary ones
situated in front to the right and left. There is a prominent lateral
bud in the axil of the plumule-sheath. In all other respects it resembles
the tribe Bordew.
35
Tribe Bambtjse^.
A small plant of Arundinaria falcata bloomed in the Cornell nursery
during the summer of 1898. About a dozen fruits were secured and
sections of the embryo made.
The fruit is oval and is covered by a pericarp, which easily separates
from the endosperm and embryo. The embryo is small, with its scutel-
lum almost completely surrounding the plumule (fig. 74, PI. VIII). The
vascular bundle traversing it is branched in all directions, as shown in
any of the transverse sections (fig. 76 A-J, PI. VIII).
The plumule-sheath differs from all other fruits of the Graminew
investigated in having five vascular bundles instead of two. At its
apex there is a well-marked slit or opening and only two vascular
bunches (fig. 70 0). Figs. 76 D, E, F show the position of the five vas-
cular bundles inclined toward the exterior side of the embryo.
The leaves have seven vascular bundles and are arranged as in all
grass embryos (fig. 76 E). The epiblast is large and broad, but does not
extend far up on the plumule. Toward the base it is rectangular in
cross section (fig. 76 G, H). The axis terminates in one large radicle
(fig. 76 K).
RELATIONSHIP AND SYSTEMATIC CONNECTION OF THE TRIBES.
Botanists disagree very generally as to which are the most primitive
tribes of the grasses. The three great authorities on the subject are
Hackel, 1 Bentham, 2 and Warming. 3 Their classifications are as follows :
bentham's classification.
A. Panicacece.
Tribe I. Panicese.
II. Maydese.
III. Oryzese.
IV. Tristeginese.
V. Zoysiese.
VI. AndropogoneiB.
B. Poacew.
Tribe VII. Phalaridete.
VIII. Agrostidese.
IX. Isaohnese.
X. Avenese.
XI. Chloride®.
XII. Festucese.
XIII. Hordeas.
XIV. Bambusese
hackel's classification.
A. Panicaeew.
Tribe I. Maydese.
II. Andropogonese.
III. Zoysiese.
IV. Tristeginese.
V. Panicese.
VI. Oryzese.
B. Poacece.
Tribe VII. Phalaridete.
VIII. Agrostidese.
IX. Avenese.
X. Chloridese.
XI. Festucese.
XII. Hordese.
XIII. Bambusese.
•Hackel, E. Echte Grseser. Engler and Prantl, Pflanzenfamilien, 2 2 : 2.
Eng. trans, by Scribner and Southworth, 1890.
3 Beutham, Geo. "Notes on Graminese," Jour, of the Linn. Soc, 19: 14-134, 1881-S2.
'Warming, E., and Potter, C, Systematic Botany.
36
warming's classification.
Tribe 1. Bambuseae.
Tribe VII. Agrostideae.
II. Oryzeae.
III. Maydese.
IV. Andropogoneae.
V. Festucese.
VIII. Phalaridea;.
IX. Chloride*.
X. Paniceae.
XI. Hordeae.
VI. Aveneae.
It will be noticed that Hackel's arrangement is in the main similar
to that of Bentham, while Warming's varies, omitting the tribes Zoy-
siew and Tristeginew. Bentham, on the one hand, regards the tribes
Panicew, Maydece, and Oryzece, while on the other, Hackel places the
Maydece, Andropogonew, and Zoysiew as the most primitive of the
grasses. Warming, however, presents an entirely different view, and
regards the Bambmew and Oryzew as the most primitive.
This great difference of opinion is probably due to the fact that the
grasses have been largely studied from the basis of only a single char-
acter. Hackel 1 claims to have discovered the magic spell by which all
difficulties must come to an end in regard to the arrangement of the
genera of the Andropogonew, but it is to be doubted whether the same
can be said of his arrangement of the tribes. The Andropogonew
together with the May dew, Panieew, Tristeginew, and Zoysiew without
doubt represent a very natural group of the Oraminew, but it is a ques-
tion whether they are the most primitive. If one studies the Andropo-
gonew from the standpoint of their resemblance to other Monocotyle-
dons one is unable to find the slightest trace of such resemblances in
any of the genera, while among the Bambusew and Oryzew there are
many similarities.
The Bambusew are characterized as large, often tree-like, grasses,
with woody, rarely herbaceous culms. The leaves are broad, some-
times compound and usually petioled. There are from three to six, or
many, stamens while the prevailing number in the other Oraminew is
two or three. Usually three remarkably large lodicules 2 are present
on the rhachilla. There is great variation in the structure and in the
form of the fruit. Both Muuro 3 and Hackel 4 use fruit characters to
divide the different genera into sections. They may be classified as
the berry-bearing and the true bamboos, the latter with linear or
oblong-linear fruits, like those of Avena and Triiicum, with a distinct
furrow down one side and the scutellum visible below.
In the berry-bearing bamboos the caryopsis appears to be contained
in an envelope somewhat analogous to the sac or perigynium which
incloses the seed of Carex. In Melocanna bambusoides this covering
'Hackel, E., Andropogonew. De Candolle's Monographic Phaner.
'Eowlee, W. W. The Morphological Significance of the Lodicules of Grasses.
Bot. Gaz. 25 : 199-203. 1898.
'Munro, Memoir on Bambuseae. Trans, of the Linn. Soc. xxvi:
4 Hackel, E., Echte Graeser. Engler andPrantl, Pflanzenfamilien, n 2 : p. 92. Eng.
trans, by Scribner and Southworth.
37
becomes very fleshy and the fruit attains the size of a large pear.
Schizo8tachyum acutiflorum has very curious bundles of hairs on the
scutellum, and the pericarp of the oblong fruit is quite loose and rugose.
Some of the genera of the section Triglossece approach very closely in
the structure of the spikelet the tribe Panicece.
The Oryzece may be compared with the Bambmece. In regard to their
leaves there is a great variety of forms, from broad, ovate, petiolate
leaves in Pharm, to long, linear ones in Zizania, and short, narrow
leaves rounded at the apex in Hydrochloa. There is also great varia-
tion in the inflorescence. In some of the genera a number of bracts are
arranged spirally around the main axis, while in others the inflores-
cence is inclosed in a spathiform envelope. The normal number of
stamens is six, although they vary from one to eight. The i>istil
usually branches into two plumose stigmas, with occasionally a three-
branched style, as in Pharm. The lodicules vary from 2 to 3. There
are long, linear fruits, as in Pharm, and oblong-linear fruits, as in Oryza.
The Oryzece therefore resemble the Bambmece in the following respects:
(1) They show great variation in the structure of their fruit and spike-
let. (2) Both have remarkably large epiblasts. (3) Some genera have
the same number of lodicules. (4) Pharm has a style with three stig-
mas. (5) Many of the genera have broad petiolate leaves and transi-
tions between these to linear ones. (6) They have to a great extent the
same geographical distribution, the larger number of the genera being
indigenous to tropical America. It would appear therefore that the
Oryzece are closely related to the Bambmece, and that together they
represent the most primitive of the grasses, thus bringing them nearer
to the other Mouocotyledons (e. g., Palmacece). So far as it has been
observed there appears to be no similarity between the Bambmece and
Hordece, although they are looked upon by both Bentham and Hackel
as being closely allied.
The Zoysiece, Tristeginece, Andropogonece, May dew, and Panicece, both
according to the characters of the fruit and those of the inflorescence,
according to Hackel's classification, form another natural group, joined
to the Oryzece through the Zoysiece and Tristeginece. The Chloridece,
although regarded by both Hackel and Warming as being removed
some distance from the Andropogonece, are like them in their fruit
characters.
The remaining tribes, Phalaridece, Agrostidece, Avenece, Festucece, and
Hordece, from their fruit characters, form another group in the order
named, which corresponds with the classification given by Hackel.
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EXPLANATION OF PLATES.
Plate I.
Fig. 1. Coix lachrymce-johi, long. sec. ; (x 7).
2 A-D. Coix lachrymm-jobi, cross sec. of embryo ; (x 9).
3. Zea mays, long. sec. of embryo; (x 5). .
4 A-F. Zea mays, cross sec. of embryo; (x 14).
5. Tripsacum dactyloides, long. sec. facing embryo; (x 8)
6. Tripsacum dactyloides, long. sec. ; (x8).
7 A and B. Tripsacum dactyloides, cross sec. ; (x 8).
Plate II.
8. Euchloma mexicana, long. sec. of embryo; (x 23).
9. Andropogon saccharatus, long, see ; (x 19).
10 A-C. Andropogon saccharatus, cross sec. ; (x 34).
11. Apluda cristata, long, sec; (x 12).
12. Apluda cristata, cross sec. ; (x 30).
13 A-E. Anthephora elegans, long, and cross sec. ; (x 17).
14 A-D. Zoysia pungens, long and cross sec. ; (x 12).
15 A-D. Perotis latifolia, long, and cross sec. ; (x 17).
16. Pennisetum spicatum, long, sec; (x 12).
17. Pennisetum spicatum, cross sec. ; (x 16).
18. Pennisetum spicatum, cross sec. ; (x 28).
Plate III.
19. Chastochloa macrochteta, long. sec. ; (x 13).
20. Paspalum pubiflorum glabrum, long. sec. ; (x20).
21. Paspalum pubiflorum glabrum, cross sec. ; (x 12).
22. Zizania aquatica, long, sec; (x 5).
23 A and B. Zizania aquatica, cross sec; (x 10).
24 A-T. Zizania aquatica, cross sec. of embryo; (x 6).
Plate IV.
25. Lygeum spartum, long. sec. ; (x 6.5).
26 A-E. Lygeum spartum, cross sec; (x 18).
27. Oryza sativa, long, sec; (x 7).
28. Homalocenchrus oryzoiC.es, long. sec. ; (xl4).
29. Anthoxanthum odoratum, long. sec. ; (x 23).
30. Stipa tenacissima, long. sec. ; (x 20).
31. Stipa tenacissima, cross sec. ; (x24).
32. Stipa viridtda, long, sec; (x 14).
83. Stipa viridula, cross sec. ; (x 42).
34. Eriocoma cuspidata, long. sec. ; (x 17).
35. Eriocoma cuspidata, cross sec. ; (x 43).
44
Plate V.
Fig. 36. Stipa riehardsoni, long. sec. ; (x 17).
37 A and B. Stipa riehardsoni, cross sec. ; (x 24).
38 A. Oryzopsis micrantha, long, and cross sec. ; (x 14).
38 B. Oryzopsis micrantha, long, and cross sec. ; (x 29).
I 39. Cinna arundinacea, long. sec. ; (x 10).
[ 40. Cinna arundinacea, cross sec. ; (x50).
41. Phleum pratense, long. sec. ; (x 18).
42. Ammophila arenaria, long. sec. ; (x 20).
43. Brachyelytrum erectum, long. sec. ; (x 6).
44. Arena sativa, long. sec. ; (x 5).
45. Arena sativa, long. sec. facing embryo; (x 6).
46 A and B. A vena satira, cross sec. ; (x 10).
47 A-G. Arena sativa, cross sec. of embryo; (x 13).
Plate VI.
48. Avena satira, long. sec. of embryo; (x 13).
49. Arrhenatherum elatius, long. sec. ; (x 11).
50. Danthonia spicata, long. sec. ; (x 17).
51. Bolcus lanatus, long. sec. ; (x 20).
52 A-D. Eleusine coracana, long, and cross sec. ; (x 13).
53. Spartina gracilis, long. sec. ; (x 9).
54 A-C. Spartina gracilis, cross sec. ; (x 16).
55. Astrebla pectinata, long. sec. ; (x 20).
56. Leptochloa imbricata, long. sec. ; (x 27).
57. Cynodon dactylon, long. sec. ; (x 31).
58. Bulbilis dactyloides, long. sec. ; (x 18).
59. Bulbilis dactyloides, cross sec. ; (x 18).
60. Beekmannia erucaformis, long. sec. ; (x 26).
Plate VII.
61. Uniola latifolia, long. sec. ; (x 10).
62. Panicularia aquatica, long. sec. ; (x 17).
63. Desmazeria sicula, long, sec; (x 17).
64. Cynosurus cristatus, long. sec. ; (x 16).
65. Hordeum vulgare, long, sec of embryo; (x 9).
66 A-H. Hordeum vulgare, cross sec. of embryo; (x 18).
67. Secale montanum, long. sec. ; (x 15).
68 A and B. Secale montanum, cross, sec; (x 14).
69. Triticum wstivum, long. sec. of embryo; (x 13).
Plate VIII.
70. Lolium rigidum, long, sec; (x 16).
71 A-C. Lolium rigidum, cross sec. ; (x 24).
72. Elymus virginicus, long. sec. ; (x 11).
73. Elymus virginicus, cross sec. ; (x 32).
74. Arundinaria falcata, long. sec. of embryo parallel to scutellum; (x 19).
75. Arundinaria falcata, long. sec. of embryo; (x 16).
76 A-K. Arundinaria falcata, cross sec. of embryo; (x 29).
o
But. 1 9, Div. of Agrostology.
Plate I.
Structure of the Caryopsis of Grasses.
Bui. 19, Div. of Agrostology.
Plate II.
Structure of the Caryopsis of Grasses.
Bui. 19, Div of Agrostology.
Plate III.
Structure of the Caryopsis of Grasses.
Bui. 19, Div. of Agrosto'ogy.
Plate IV.
Structure of the Caryopsis of Grasses.
Bui. 19, Div. of Agrostology.
Plate V.
Bui 19, Div. of Agrostology.
Plate VI.
Structure of the Caryopsis of Grasses.
Bui. 19, Div. of Agrostology.
Plate VII.
Structure of the Caryopsis of Grasses.
Bui. 19, Div. of Agrostology.
Plate VIII.
Structure of the Caryopsis of Grasses.
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