THE SEED. 



155 



physiology ; and therefore the word perisperm is preferable. All seeds in 

 their rudimentary condition contain perisperm j but as the embryo grows 

 it is often absorbed, so that in the ripe seed it is no longer perceptible. 

 It is considered to be analogous with the prothallus of the higher Crypto- 

 gams. 



The Perisperm varies very much in both quantity and in texture 

 in proportion to the relative magnitude attained by the embryo 

 (figs. 313 & 320), and in consequence of the different mode of 



Fig. 319. 



Fig. 317. 



Fig. 318. 



Fig. 317. Section of the seed of Lychnis, with a peripherically curved embryo, 6, surrounding 



the perisperm, a. 

 Fig. 318. Section of the seed of Piper, showing the embryo in a separate sac at the apex 



of the perisperm, which latter is hollow in the middle. 

 Fig. 319. Section of the fruit of the Cocoa-nut Palm, showing the fibrous epicarp, the woody 



endocarp (ar) enclosing the hollow perisperm, in which lies the minute embryo. 



development of the cellular tissue and its contents in different 

 cases. 



The texture or consistence of the perisperm is termed mealy 

 or farinaceous when it may be readily broken down into a starchy 



Fig. 322. 



Fig. 321. 



A 



-e 



Fig. 320. Vertical section of the seed of JRicinus : a, hilum ; 6, micropyle ; c, raphe ; d, chalaza 



e, embryo ; f, perisperm. 

 Fig. 321. Aperispennie dicotyledonous seed of a Bean, with the coats removed: a, radicle; 



b', b", cotyledons (separated to show the plumule, c). 

 Fig. 322. Monocotyledonous embryos removed from the perisperm, vertically sliced: A, of 



Calla palustris ; B,Avena(O&t): a, radicle; b, cotyledon; c, plumule. 



powder (as in Corn-grains &c.); oily when it is composed of soft 



