\ 



l66 BOTANICAL GAZETTE [m. 



egg in Nephrodium accords with Thom's and Shaw's accounts. The 

 presence of the resting nucleus including both maternal and paternal 

 chromatin within a common nuclear membrane as described in 



phr odium 



Ikeno (43, 44) in Cycas and 



forms 



union 



two 



There is only one paper that gives details of fertilization in a 

 br}'oph}1:e, a contribution by Kruch (56) on Riella. In this form 



orsran- 



m 



This differs from the condition in Nephrodium^ for the sperm does 

 not enter into the egg nucleus, but two nuclei fuse side by side with 

 their chromosomes fully organized. 



With respect to the cytoplasmic structures of the sperm, all inves- 

 tigations among cycads and in Ginkgo agree that they are left behind 

 in the c\1;oplasm of the essr before the gamete nuclei unite. A 



limil 



ported in both Adiantum and Aspidium. In 



cannot confirm 



— ^ — ^ . — .. , 



obsened in which the blepharoplast was not left behind in the cyto- 

 plasm. However, such cases do not of course necessarily mean that 

 this stnicture takes part in what may be regarded as an essential part 

 of the process of fertilization. 



Conclusion 



Since the present investigation on spermatogenesis, oogenesis, and 

 fertilization, together with the preceding study on sporogenesis, has 

 been made to trace out the complete histor}^ of the chromosome in 

 the normal life-cyde of Xephrodium as preparatory to the study of 

 apogamy, the general conclusions will be given in the subsequent 

 paper. However, the two principal points established by the present 

 investigation may be stated here : (i) the countmg of the number of 

 Chromosomes is possible in the gametoph\-te ; (2) the number of the 

 chromosomes in the gametoph\te is constant (6a or 66>. 



In closing I wish to express my thanks to Professor John -M. 

 CotJXTEs. and Doctor Charles J. Chamberlain who gave important 

 advice and valuable suggestions in the course of the study. 



