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. 378. — ^Lonitudinal section of a grain of wheat (Triticum vulgarc). 

 p.s.c, pericarp and s'eed-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- 



