CHAPTER XV 

 THE ENDOSPERM IN INHERITANCE 



We have dealt chiefly with inheritance in the sporo- 

 phyte, in connection with which most work in plant 

 genetics has been done. Brief mention has been made of 

 inheritance in the gametophyte, in connection with which 

 there has been very little work. It is natural now to 

 consider inheritance in the endosperm. This classifica- 

 tion raises the question as to the nature of the endo- 

 sperm. In general it has been regarded as belonging 

 to the gametophyte generation, but since the discovery 

 of " double fertilization'' in 1898 some 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 the 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 characteristic 

 of a gametophyte, others characteristic of a sporophyte, 

 and still others peculiar to itself. Judgment as to its 

 nature, therefore, will depend upon which of these 

 features are emphasized. 



It is generally believed that angiosperms have been 

 derived from gymnosperms, and it is natural therefore 

 to explain angiosperm structures by the corresponding 

 structures of gymnosperms. The gymnosperm and 

 angiosperm ovules are contrasted in fig. 34, which will 

 assist in the following discussion. In gymnosperms the 



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