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 
seutellum 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 Maydew, Chloridee, Panicew, and Andropogo- 
nec 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 aecord- 
ance with Hackel’s classification of the tribes with reference to the 
Chloridea. 
HOMOLOGY OP THE PARTS OF 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 regarded 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. Hanstein concludes that it is merely 
an insignificant trichomatic 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! 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 
Graminew are in reality dicotyledons, which have accidentally become 
monocotyledons. : 
In dicia of the faet 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- 
chrus, Zizania, and Oryza, where they are inserted on the axis opposite 
the insertion of the scutellum. 
! Comptes Rendus seanc. l'acad. des Sciences, 124 : 1896-97. 
