CHAPTER XI 

 THE ENDOSPER]\I IN INHERITANXE 



We have dealt chiefly with inheritance in the sporo- 

 phyte, in connection with which most of the work in 

 plant genetics has been done. Brief mention has been 

 made of inheritance in the gametophyte, on which there 

 has been very little work. It is appropriate now to con- 

 sider inheritance in the endosperm. This classihcation 

 raises the question as to the nature of the endosperm. 

 It was at one time generally regarded as belonging to the 

 gametophyte generation, but since the discovery of 

 "double fertilization" in 1898 many have claimed that it 

 belongs to the sporophyte generation. On the basis 

 of chromosome numbers, it is neither, so that there is 

 also the claim that endosperm is neither sporophyte nor 

 gametophyte; at least we are justified in considering 

 inheritance in endosperm as a separate topic. As might 

 be inferred, endosperm shows some features character- 

 istic of a gametophyte, others characteristic of a sporo- 

 phyte, and still others peculiar to itself. Judgment as to 

 its nature, therefore, will depend on which of these fea- 

 tures is emphasized. 



It is generally believed that angios})erms have been 

 derived from gymnosperms, and it is natural therefore 

 to explain angiosperm structures by the corresj)onding 

 structures of gymnos])erms. 11ie gyninosj)erni and angio- 

 sperm ovules are contrasted in fig. 2^, whicli will assist 

 in the following discussion. In gymnosperms the situa- 



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