20 
widely separated from the scutellum in many grasses. See Zizania and 
Homalocenchrus (figs. 22 and 28, Pls. III 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. 388A, Pl. V) and Stipa 
richardsonii (fig. 36, Pl. V), or, again, completely horizontal, as in 
Eriocoma (fig. 34, Pl. IV), Oryza sativa (fig. 27 , Pl. IV), and Eleusine 
(fig. 52A-D, Pl. VI. In Homalocenchrus oryzoides (fig. 28, Pl. IV) it 
has a slightly upward tendency. 
There are, however, embryos with numerous lateral roots. Triticum 
estivum (fig. 69, Pl. VII) has four lateral roots, two on each side of the 
scutellum. Zizania (fig. 240-Q, Pl. III) has three, situated directly 
under the plumule, a long distance from the main radicle. Cois (fig. I, 
Pl. I) has four radieles, 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, G .and H, Pl. VII) has eight secondary 
radicles, three on each side of the scutellum and two in front. On 
germination the primary radiele 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 in the radicle. The rooteap 
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 seutellum. In dissecting out the embryo the radicle or radicles, 
with their rooteaps, 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 Hordec there is a lateral bud in 
the axil of the plumule-sheath: Hordeum (fig. 65, Pl. VIT), Triticum (fig. 
69, Pl. VID, Elymus (fig. 72, Pl. VIII) and Secale (fig. 67, Pl. VII). 
Bruns regards this as proving that the plumule-sheath must represent 
a leaf. Similar buds, however, may be found in Polygonum, Rumes, 
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 Avenew, while all other genera in which lateral buds have | 
been found belong to the tribe Hordec. Bruns, however, figures psc : 4 
uarie: a Bambusa with a large lateral bud in the axil of the plumul 
ea 
