526 



THE AMERK AX X A ICR A Lis '/' [Vol. XLIV 



These results from studies on the three most highly 

 differentiated groups of the Phaeophycese (Dictyotales,. 

 Fueales and OutleriaceaO indicate how complex has been 

 the evolutionary history of the divergent phyla as- 

 sembled under this name, and how difficult are likely to 

 be the problems of tracing their relationship to lower 

 groups of the brown alga'. 



Perhaps in no assemblage of the alga 4 have the cyto- 

 logical studies of recent date given such striking results 

 as in the Rhodophyeea?. Our understanding of the life 

 history of these forms has been quite revolutionized by 

 the research of three investigators, Wolfe, Vamanouchi 

 and Lewis. 



Wolfe 13 from studies on Xewalioit determined for this 

 type that the sexual organs are not simple uninucleate 

 cells, since the triehogyne possesses a nucleus in addition 

 to that in the carpogonium and the sperm is binucleate 

 and the homologue of the antheridium. The cells of the 

 cystocarp following the fertilization of the carpogonium 

 have nuclei with approximately sixteen chromosomes 

 which is double the number present in the vegetative 

 cells of the parent, plant. The cystocarp must then be 

 regarded as sporophytic in character. Because the 

 mitotic figures in advanced stages of the cystocarps 

 showed certain peculiarities Wolfe concluded that a re- 

 duction of the chromosomes occurred preliminary to the 

 development of the carpospores. However, he did not 

 trace a process of chromosome reduction through the 

 characteristic phase of synapsis followed by a hetero- 

 typic mitosis, and on this point of his investigation more 

 evidence is to be desired. There are certain reasons 

 why in life histories among the Rhodophyceae of the type 

 of Nemalion the process of chromosome reduction may 

 be expected to occur at the time of the germination of the 



