158 HISTORY OF BOTANY 



that the gametophyte produced one much reduced 

 archegonium, the so-called " egg apparatus," and that 

 the gametophytic tissue, at first extremely scanty in 

 amount, was stimulated to renewed growth after fertili- 

 sation, and formed what we call "endosperm." The 

 synergidae were, on the other hand, interpreted as 

 potential ova by Dodel in 1891, a view that was supported 

 by several investigators who had found that these cells 

 might give rise to accessory embryos. 



Fertilisation 



During the last thirty years of the nineteenth century 

 the process of fertiUsation was cleared up, more especially 

 by Strasburger, who, in 1884, observed the fusion of one 

 of the nuclei from the pollen tube with the nucleus of the 

 ovum, the other pollen nucleus evidently degenerating. 

 In 1898, however, Nawaschin showed that the second 

 generative nucleus did not degenerate, but that it entered 

 the embryo-sac and fused with the so-called " definitive 

 nucleus of the embryo -sac," a phenomenon that was 

 termed by its discoverer " double fertilisation." This 

 gave rise to the view that the endosperm was not a much 

 delayed gametophyte but really a second and greatly 

 modified embryo, an interpretation that was believed to 

 be supported by the peculiar condition known as " xenia." 

 In 1867 Hildebrandt noticed that when yellow maize 

 was crossed with brown maize both the embryo and the 

 endosperm exhibited hybrid characters. It was thought 

 that this pecuharity in the endosperm might be accounted 

 for on the theory that the fusion of the second generative 

 nucleus with the embryo-sac nucleus was sexual in its 

 nature. 



To complete the story, Hanstein, Famintzin, and 

 others, between 1869 and 1890, traced the development 

 of the embryo both in Monocotyledons and Dicotyledons, 

 and showed that only part of the oosperm gave rise to 



