CORN KERNEL 63 
The location of the embryo at one side of the endosperm, instead 
of being centrally located and surrounded by the endosperm, is a 
peculiar feature of the Grass type of seeds. 
The embryo consists of two main parts: the large scutellum or 
cotyledon (cot) which lies in con- 
tact with the endosperm, and the 
embryonic axis which upon germi- 
nation produces the stem at its 
upper and roots at its lower end. 
The axis is attached along its 
central region to the cotyledon, 
which supplies it food during 
growth. At the upper end of the 
axis is the plumule, a small bud- 
like structure consisting of a grow- 
ing point (gr) and some small 
leaves (1). The plumule is en- 
closed in a sheath (ct) called col- 
copie. Between the. pltmule Fic. 66. — Section through a ker- 
and the attachment of the ely ~ nel of Corn. cot, cotyledon; ep, epi- 
ledon is a short stem (st), which thelial layer of cotyledon; ct, coleop- 
with the plumule is often called tile; gr, growing point of plumule; 
epicotyl (the portion above the J, young leaves; st, epicotyl; r, radi- 
cotyledon). The portion of the le: 7% Toot cap; cr, coleorhiza; n, 
2 : soft endosperm; h, hard endosperm; 
axis below the cotyledon consists é, eoverde called Getidaees, “Muah 
chiefly of the radicle (r), the struc- enlarged. 
ture which develops the first root. 
The radicle bears at its tip the root cap (rc) and is enclosed by 
the coleorhiza (cr). 
The hypocotyl, which is all or only a part of the axis between the 
plumule and radicle (a point in dispute among botanists), is the 
portion of the axis developing least when the embryo resumes 
growth. In the Grasses there is very little elongation of the hypo- 
cotyl and, consequently, the establishment of the young plant in 
the soil and light depends mainly upon the growth of the radicle 
and plumule. The fact that the hypocotyl remains small while 
the radicle, since it forms the first root, becomes a prominent 
structure, accounts for the general application of the term rad- 
icle to all of the lower portion of the axis, and the rare use of the 
term hypocotyl! in connection with grass embryos. 
