248 THE AMERICAN NATURALIST. |. (Vor. XXXIX. 
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 (: 00a ; 
: oob), in the tissue preliminary to spore formation. He also con- 
firmed Dangeard ('94—'95c) 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 (:02) 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 (:02) as are also the detailed studies of 
Ruhland (:01) on a number of forms and Bambeke (:03). 
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 oóspore 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 (: o1) 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 
