182 MORPHOLOGY OF ANGIOSPERMS 



act of the male nucleus is a case of true fertilization, the infer- 

 ence being that the endosperm is a second embryo or sporophyte, 

 as Le Monnier had suggested. 



Strasburger 37 in discussing the whole subject concludes that 

 the triple fusion is not real fertilization. Of course in such a 

 discussion much depends upon the definition of fertilization. 

 Strasburger distinguishes between " generative fertilization " 

 and " vegetative fertilization/' the former being a definite 

 union of parental qualities and resulting in an embryo, the 

 latter a fusion resulting merely in a growth-stimulus. He 

 thinks that the endosperm is historically a gametophyte, and 

 that the fusion which initiates it has no origin in an act of 

 fertilization. 



Later, Miss Sargant 38 published an admirable resume of 

 the subject, together with a clear statement of the problems 

 involved and certain suggestions by way of interpretation. She 

 very justly states that if the endosperm " arose from a belated 

 formation of prothallus, we must trace the origin of the triple 

 nuclear fusion which precedes its development " ; and if it is 

 a modified embryo " we have to account for the interference of 

 the lower polar nucleus with the act of fertilization, and for 

 the subsequent development of a body unlike a normal embryo." 

 Her suggested interpretation of the phenomenon is that the 

 fusion of the male nucleus with the micropylar polar nucleus, an 

 undoubted female nucleus, both containing the reduced number 

 of chromosomes, is a typical sexual union; but that the antip- 

 odal polar nucleus, with its vegetative character, and indefi- 

 nite and usually increased number of chromosomes, is a disturb- 

 ing factor, and the result is not a normal embryo but a small 

 and short-lived mass of tissue. She aptly cites the experiments 

 of Boveri 13 with sea-urchins, in forcing more than one sperm- 

 nucleus to unite with a single egg-nucleus and producing mon- 

 strous larval structures. " The presence of the third nucleus, 

 therefore, with its redundant chromosomes, serves to secure the 

 degeneracy of the resulting tissue." This means, of course, that 

 the endosperm is a degenerate embryo, and that the triple 

 fusion is a true sexual union whose normal result has been 

 interfered with by the presence of a non-sexual nucleus in the 

 combination. 



It is impossible to solve such a problem by a discussion of 



