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 7 8. -Longitudinal section of a grain of wheat (Triticum vulgare), 

 P+s,c., pericarp and seed-coats (united); en, endosperm; al, aleurone layer; 

 gl, glandiHar 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- 



