179 
the Embryo and Seedling in the Gramineae. 
Arena itself is, as we have already said, the most complete specimen of 
its type. Zizania aquatica , L., the Manchurian Water-Rice, deserves special 
attention on account of the simple structure of its first node, in which we 
think it approaches the primitive type. We have also described two other 
Grasses of the Arena type for comparison : Lolinm italicum , A. Br., and 
Leersia oryzoides , Sw. 
Zizania aquatica , L. The fruits are long and slender. They will 
germinate only while quite fresh, and when planted under water. The 
vascular ground-plan of the seedling is like that of Arena . The numerous 
differences in detail can generally be referred to 
the adaptation of Zizania to an aquatic habit. 
The endosperm of Zizania is scanty compared 
with that of Arena satira , in which—as in all 
cultivated cereals—it is unnaturally bulky. The 
scutellum is like a linear leaf in outline. It is 
separated from the coleoptile by a very long and 
slender mesocotyl (Text-fig. 18, and PI. IX, 
Fig. 6). As in Arena , the scutellum trace runs 
upwards to the first node side by side with the 
mesocotylar stele, but is perfectly distinct from it 
throughout. 
The stem-bud is wrapped in a linear leaf-like 
coleoptile ; its margins united into a short tubular 
sheath at the base (PI. IX, Fig. 6). There is 
no stiff pointed cap such as that which protects 
the early leaves of Arena and other terrestrial 
Grasses. But two bundles run nearly the whole 
length of the coleoptile, and, seen in transverse 
section, they occupy the same relative positions 
as in Arena , and recall the two-nerved ‘axillary 
stipules ’ found in some species of Potamogeton} 
We consider the mesocotyl of Zizania , like 
that of Arena, to represent a fusion of the cotyledonary stalk with the 
hypocotyl. If we mentally reconstruct a form in which they were separate 
1 Cf. the description given by E. Cosson (Note sur la stipule et la prefeuille dans le genre 
Potamogeton , et quelques considerations sur ces organes dans les autres monocotylees. Bull, de la 
Soc. Bot. de France, t. vii, p. 715, i860) : ‘La stipule, dans la plupart des Potamogeton, est con¬ 
stitute par un organe indivis, membraneux, libre, de forme et de longueur variables, insere a l’aisselle 
de la feuille, a face superieure regardant du meme cote que la face superieure de la feuille correspon- 
dante, et entourant d’une maniere plus ou moins complete la base de l’entre-noeud de la tige. . . 
Cette stipule axillaire prtsente, surtout dans les especes a feuilles petiolees, deux nervures presque 
paralleles, saillantes, generalement en forme de carene, placees exactement a la limite du point de 
contact du petiole. Assez souvent cette stipule n’est binerviee et bicarenee que dans sa partie 
inferieure, et quelquefois meme elle n’est nullement binerviee.’ 
N % 
size. 
