MORPHOLOGY OF HIGHER PLANTS. 



219 



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

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

 lifene it is as large as the cotyledons. 



H M 



J! 





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

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

 Longitudinal 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. 

 I'ransverse 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 



