25 
The third view is that the plumule-sheath is a ligule like growth pro- 
ceeding from the scutellum as au inseparable part. The existence of 
an intermediate part between the insertion of the plumule-sheath and 
that of the seutellum in many embryos, is relied upon by Bernhardi, 
Bruns and others as positive proof that there can be no connection 
between these organs. By many authors it has been called an inter- 
node, whieh latter always develops between two leaves and not between 
two parts of a leaf. 
Bruns says that while in Euchlena 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 distinetly in Zizania 
and Homalocenchrus, and not at all in the genera of the Agrostidea, 
is nothing but the first unusually lengthened node. The ligule-like 
growth, the plumule-sheath, is usually inserted directly over the scutel- 
lum, but sometimes the axis stretches itself between the insertion ot 
the scutellum and the plumule-sheath as in the mature fruits of Zizania, 
Homalocenchrus, the Chloridea, 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! 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. i 
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. DE 
Comparing the eulm leaf with the scutellum and singes , the 
cotyledonary leaf of the embryo, one finds that the latter > no 
sheath. Its sessile blade, however, elongates to form the scute "n 
while the pumule-sheath, which is homologous with the ligule, SIES 
a great size with vascular bundles similar to the ligule of — a 
arenaria. It is provided with two prominent lateral nerves, whie 
i rophyll and stomata. : : 
d iu parts may in the same manner be carried aed i 
the spikelet. The awn of the floral glume, when present, I$ rega 
i he leaf, and therefore to the scutel- 
as corresponding to the blade of t x Xs Work of tbe 
lum of the embryo. When the awn 1s inserted on the bac 
1 Anatomie de l'arete des Graminees 
1871. 
23 OU SN M DURUTSSN CEDE 
Mem. de l'ae. des Sci. et lettres. Montpellier. 
