494 
STRUCTURE AND LIFE HISTORIES 
tains endosperm, with the embryo located at one side 
(Figs. 378 and 83). The cotyledon (scutellum) serves to 
secrete enzymes that digest the endosperm, and then 
FIG. 3 78. -Longitudinal section of a grain of wheat (Triticum vulgare). 
P.S.C., pericarp and seed-coats (united); en, endosperm; al, aleurone layer; 
gl, glandular layer of the scutellum; sc, scutellum; sp, sheath of plumule 
(coleoptile); pi, plumule; r.cot., rudimentary cotyledon; ra, radicle; re, 
root-cap; r.s., root-sheath (coleorhiza). (From microscopical preparation 
of E. W. Olive.) 
absorb the digested food by osmosis (Fig. 62). The cylin- 
drical stems are jointed and usually hollow (except at the 
joints) . The leaves are usually long, slender, and parallel- 
