i FERTILISATION AND EMBRYOLOGY 13 



consisting of some hundreds of cells, and exhibiting a 

 cordate from under the microscope (Fig. 28). The 

 pointed end becomes the radicle, and the two lobes develop 

 into two cotyledons, marked with black dots caused by 

 the presence of the resin-glands which are characteristic 

 of all portions of the cotton plant other than the root. 

 The adult cotyledons are folded in a complex way, being 

 considerably broader than the seed in which they are 

 contained, and they envelop the straight radicle. Their 

 cells contain much of the food reserves in the form of oil, 

 which is an important commercial product. The endosperm, 

 formed by rapid division of the triple nucleus, is destroyed 

 during the growth of the embryo, so that the ripe seed is 

 ex-albuminous. 



We shall postpone consideration of the seed coat, and 

 of the development of the lint upon it, to its proper place 

 at the end of the story of the individual. 



