No. 503] NOTES AND LITERATURE 



745 



The most recent cytologieal contribution to the study of 

 apogamy in the ferns is by Yamanouchi. 2 This paper gives a 

 much more detailed account of nuclear structure and the be- 

 havior of chromosomes than that of Farmer and Digby, and is 

 remarkable for the thoroughness of the sludy of critical phases 

 throughout the entire life history. We have already noticed 

 a portion of the work in the review of some recent research on 

 cilia-forming organs of plant cells in the August number of the 

 Naturalist. Yamanouchi worked upon Nephrodium molle 

 which has the advantage of presenting under ordinary condi- 

 tions of culture the normal life history of ferns. The apogamous 

 development of sporophytes may. however, be readily induced 

 in prothallia exposed to direct sunlight and watered from below 

 so as to prevent the possible escape of sperms and fertilization 

 of archegonia. Such prothallia develop much more slowly than 

 under normal conditions. After six weeks the cushion regions 

 become markedly thickened, which thickenings indicate the be- 

 ginnings of apogamous sporophytes. 



Yamanouchi made very accurate counts of the chromosomes 

 throughout the critical phases of the normal life history pre- 



reduced during sporogenesis to 64 or 66 in the usual manner. 

 The gametophyte has then 64 or 66 chromosomes which were 

 counted in the vegetative cells of the prothallia and in the 

 mitoses leading up to the formation of sperms and eggs. The 

 fertilized egg has of course the double or sporophytic number. 



produce sporophytes apogamously, have 64 or 66 chromosomes. 

 The mitoses up to the 30-50 cell stages are similar to those in 

 normal prothallia. After that the growth is very slow and 



reference to the surface of the prothallia. The apogamous 

 prothallia produce antheridia in abundance which develop 

 motile sperms, the mitoses showing 64 or 66 chromosomes. 



thallia. Occasionally archegonia initials are differentiated, from 

 which a central cell is cut off as in normal prothallia. but this 

 central cell either remains undivided or produces eggs and canal 

 •Yamanouchi, S. Apogamy in Nephrodium. Bot. Ga~., XLV, p. 289, 



