MORPHOLOGY OF HIGHER PLANTS. 



219 



(Fig. 188) and cola, or partly developed as in strophanthus 

 (Fig. 186) ; the hypocotyl is usually small, but in the Umbel- 

 liferse it is as large as the cotyledons. 



Fig. 122. A, — Longitudinal section through anatropous seed of linum: R, raphe; SC, 

 seed-coat; M, hilum; H, micropyle; EN, endosgerm; C, cotyledon; HY, hypocotyl. B. — 

 LfOngitudinal section through stramonium seed: SC, seed-coat; H, micropyle; -M, hilum; 

 EN, endosperm; E, curved embryo. C. — Transverse section through endosperm of nux 

 vomica showing thick-walled parenchyma, the cells containing oil and protoplasm. D. — 

 Transverse section through endosperm of seed of Ricinus communis, one cell filled with 

 aleurone grains containing a crystalloid and globoid, and another in which the aleurone 

 grains have been dissolved, the cytoplasm and nucleus remaining. 



PLANT METABOLISM. 



Food of Plants. — It has already been pointed out that certain 

 of the chemical elements are necessary for the growth of plants 

 (p. 3), and that these are derived partly from the surrounding 



