CHAP, in The Morphology of the Flower 99 



nucleus the sexual function, while the true sexual nucleus 

 was thought to break up and disappear, but he elucidated 

 the true relations in his memoir of 1884. 



In this work he suggested also that the products of the 

 germination of the angiospermous pollen grain represent 

 only an antheridium, and that the prothallial tissue, 

 reduced continuously throughout the Pteridophyta, is met 

 with for the last time in the few cells cut off in the pollen 

 grain of the Gymnosperms, before the protrusion of the tube. 

 This view received very general support, and the pollen 

 tube of the Angiosperms gradually ceased to be recognized 

 as the male gametophyte, though the exact nature of its 

 homologies was in dispute at the end of the century. 



The more completely differentiated antheridium of the 

 Conifers was discovered in 1891 by Belajeff, in his researches 

 on Taxus. The homology of the structures resulting from 

 the division of the antheridial cell with the antherozoids 

 of the Pteridophyta was established, if proof were needed, 

 by the discovery of ciliated male cells in Ginkgo by Hirase 

 in 1895, in Cycas by Ikeno in 1896, and in Zamia, by 

 Webber in 1897. 



Though in the Lehrbuch the embryo sac was recognized 

 by Sachs to be the representative of the megaspore of 

 Selaginella, he did not find in its contents the homologues 

 ''of the prothallus. In the fourth edition of the Lehrbuch 

 he spoke of embryonic or germinal vesicles formed in it 

 by free-cell-formation, and of one of them, a primordial 

 cell with a large nucleus, as homologous with the oosphere 

 among Cryptogams. He said there were usually two 

 embryonic vesicles side by side in the embryo-sac, which 

 in some genera were very long and peculiarly organized, 

 the upper end projecting as a long slender tube into or 

 even beyond the micropyle. This appearance had been 

 seen also by Schacht, and by him named the ' Filiform 

 Apparatus ' ; it was considered to receive the pollen tube 



G 2 



