566 THE AMERICAN NATURALIST. [VOL. XXXIX. 



the single fusion nuclei within these reproductive cells. There 

 is much evidence that the period in the life history characterized 

 by the presence of paired nuclei represents a sporophyte phase. 



Blackman (:O4a, p. 353) regards the process by which the 

 second nucleus enters the "fertile cell," resulting in the conju- 

 gate nuclei, as a reduced form of ordinary fertilization. I have 

 already pointed out in Section IV, " Asexual Cell Unions and 

 Nuclear Fusions," what seem to me to be serious objections to 

 the use of the term fertilization when it is clear that the second 

 nucleus in the pair is morphologically not a gamete nucleus, and 

 the subject was also taken up in the account of fertilization in 

 the present section. Whatever may be the physiological inter- 

 pretation of this remarkable phenomenon it seems to me clearly 

 a substitute process for a former sexual condition and involves 

 other elements than the original gametes and as such is a typi- 

 cal illustration of apogamy. 



It seems probable that further studies in the Basidiomycetes 

 will determine a similar origin for the paired nuclei preceding 

 the basidium to that of Phragmidium but without any trace of 

 former sexual organs at least in the higher groups. And these 

 conditions must signify the complete disappearance of structures 

 representing sexual organs and the substitution of an apogamous 

 development of the sporophyte generation for the sexual act. 

 In this connection the interesting nuclear fusions in the ascus 

 are of great interest for they may hold relations to degenerate 

 sexual conditions in the Ascomycetes. 



Farmer, Moore, and Digby (103) have reported some remark- 

 able nuclear fusions preceding the apogamous development of 

 the sporophytes of Nephrodium, which have many points of 

 resemblance to the apogamous phenomena in the Uredinales 

 just described. These authors find that cells of the prothallus 

 from which the sporophytic outgrowths arise, become binucleate 

 through the migration of nuclei from neighboring cells. The 

 two nuclei may remain separate for some time or. they may fuse 

 at once. They regard the whole process " as a kind of irregu- 

 lar fertilization " by which the outgrowth destined to form the 

 sporophyte becomes supplied with nuclei containing the double 

 number of chromosomes. It seems to me unfortunate to asso- 



