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THE AMERICAN NATURALIST [Vol. XLIV 



in the basidium and teleutospore. Dangeard pronounced 

 these nuclei which fuse in the ascus the morphological 

 equivalents of the gametes of other fungi and alga? and 

 the resulting ascus a fertilized egg; a view in which he 

 has not been followed by other students of the group. 

 It seems probable, however, that this fusion functionally 

 may have the value in greater or less degree of a sexual 

 fusion, and that in eases in which the normal union of 

 gametes has disappeared this endokaryogamy may be a 

 substitute for it. 



The most puzzling feature of the sexual reproduction 

 in the ascomycetes and that about whose existence, I may 

 add, there is least agreement, lies in the fact that in the 

 course of a single life cycle we have two nuclear fusions. 

 At the origin of the ascocarp we find the formation and 

 fusion of normally developed sexual cells and nuclei and 

 in the young ascus a fusion of included nuclei. There is 

 practically no dispute at present that the gametes formed 

 at the origin of the ascocarp represent the original and 

 normal sex organs of the fungus and for Pyronema the 

 fusion between the antheridium and trichogyne is uni- 



My own studies have convinced me that in the mildews 

 and Pyronema at least we have a normal conjugation of 

 differentiated gametes at the origin of the ascocarp and 

 an endokaryogamy in the ascus. 



Blackman and Fraser confirm the existence of the two 

 fusions in Sphcerotheca and Blackman and Fraser (1906, 

 Humaria gronulata), Fraser and Chambers (1907, 

 Aspergillus Herbariorum), Welsford (1907, Ascobolus), 

 Fraser (1908. Humaria rutilans), Cutting (1909, Asco- 

 phanus) and Dale (1909, Aspergillus repens) describe 

 the occurrence of two endokarvogamies in a single life 

 cycle. 



As already noted, Claussen in a recent preliminary 

 paper attempts to resolve this difficulty in Pyronema by 

 claiming that while there is a normaf cell fusion at the 

 origin of the ascocarp the nuclei of the gametes do not 



