248 THE AMERICAN NATURALIST. [VoL. XXXIX. 



t 

 nuclei (synkaryons) and their fusion in the basidium in a large 



number of Hymenomycetes and Gasteromycetes. 



Evidence is thus accumulating that the cells in the mycelium 

 of higher Basidiomycetes (Hymenomycetes and Gasteromycetes) 

 are binucleate for extended periods previous to the formation of 

 basidia where nuclear fusions always take place. Binucleate cells 

 in the higher Basidiomycetes were first reported by Maire (: ooa ; 

 : oob), in the tissue preliminary to spore formation. He also con- 

 firmed Dangeard ('g^-'g^c) in his view that only two nuclei unite 

 in the basidium contrary to accounts of Rosen ('93) and Wager 

 ('99, p. 586) which described a succession of fusions involving 

 sometimes as many as six or eight nuclei. Harper (:O2) has 

 given for Hypochnus one of the most complete accounts of the 

 behavior of paired nuclei previous to and during the development 

 of the basidium. The cells of the mycelium of this simple 

 Hymenomycete were found to be binucleate as far back as they 

 were studied which included all of the conspicuous vegetative 

 structure. Only a single pair of nuclei enters the basidium and 

 fuses. Harper's results are then in agreement with the extended 

 observations of Maire (:O2) as are also the detailed studies of 

 Ruhland (:oi) on a number of forms and Bambeke (:O3). 

 Taken together they seem to show clearly that the mycelium, 

 for long periods preliminary to the formation of basidia, contains 

 paired nuclei and that the basidia receive each a single pair, 

 which nuclei fuse. There is thus an exact correspondence 

 between the life histories of the Ustilaginales, Uredinales, and 

 higher Basidiomycetes with respect to the period of paired 

 nuclei and their fusion in the teleutospore or basidium. 

 Dangeard called the fusion in the basidium a sexual act and the 

 structure an oospore regardless of the morphological difficulties 

 of such a conception. Maire (: 02, p. 202) states that the origin 

 of the paired nuclei is the only phenomenon strictly comparable 

 to fertilization and Blackman's studies support this view. Ruh- 

 land (:oi) regards the conditions as a deviation from the normal 

 type of sexuality calling it " intracellular karyogamy." The 

 origin of the paired nuclei is not known for any higher Basidi- 

 omycete and the discovery of this period and determination of 

 the events leading to the change from uninucleate mycelium to 



