254 THE AMERICAN NATURALIST. [VOL. XXXIX. 



Harper that the number of chromosomes presented in the 

 mitoses within the ascus is large (8, 12, 16, in various species) 

 as against Dangeard and Maire who have claimed that the 

 number is uniformly 4. Guilliermond's account of spore forma- 

 tion in the ascus supports that of Harper (described in Section 

 II) in all essentials and gives especial attention to the structure 

 of the epiplasm and its inclusions. 



In summary : the significance of the nuclear fusions in the 

 ascus seems very much of a mystery. If they could be associ- 

 ated with an apogamous development of the ascocarp we should 

 have conditions analogous to those in the Basidiomycetes but 

 following a sexual act as it does in Sphaerotheca, Erysiphe, and 

 Pyronema we find a phenomenon whose raison d' etre is not 

 apparent. However, we do not know the history of the nuclei 

 preceding the group of four at the end of the ascogenous hypha 

 and perhaps it may be discovered that events at this period are 

 concerned with nuclear reduction at the end of a sporophyte 

 generation. 



One of the most interesting announcements of recent months 

 is that in a preliminary note of Farmer, Moore, and Digby (: 03) 

 on the nuclear history preceding the apogamous development of 

 a species of Nephrodium. They found that the cells of the 

 prothallus at the point where the sporophyte arose became 

 binucleate by the migration of nuclei from neighboring cells. 

 The two nuclei might remain separate for some time or fuse at 

 once. The authors speak of the whole process "as a kind of 

 irregular fertilization" and Blackman considers it analogous to 

 the entrance of the nucleus into the fertile cell of Phragmidium 

 and the establishment of the paired nuclei in the Uredinales. 

 As we discussed the phenomenon in that connection I consid- 

 ered the use of the term fertilization unfortunate since it 

 included processes which however similar physiologically held no 

 relation morphologically and phylogenetically to normal sexual 

 processes. As stated then, it seems to me much clearer to 

 regard all such apogamous phenomena apart from sexual proc- 

 esses, pointing out as far as possible physiological resemblances 

 but recognizing the wide gap in morphology established by the 

 past evolutionary history of the plant. The interest in the phe- 



