410 
HARRY M. FITZPATRICK 
cent explanation of the maintenance of the binucleate condition in the 
Basidiomycetes advanced by Kniep (28) cannot be appHed to Eocro- 
nartiiim muscicola. The conjugate divisions in this species certainly 
take place without the assistance of clamp connections. Moreover, 
clamp connections are never found on the basidia. 
General Considerations 
The discovery in the Uredinales of sexual cell fusions accompanied 
by a well defined alternation of generations leaves no room for doubt 
that in this group of the Basidiomycetes sexuality exists. The now 
familiar observations of Blackman (2, 3) and Christman (7, 8, 9) 
have been confirmed and amplified by investigations by Olive (39, 40, 
41, 42, 43), Kurssanow (31), Hoffmann (21), Arnaud (i), Fromme (15, 
16), Kunkel (29, 30), and others on various species and on special 
phases of the cytology of the group. The mass of evidence accumu- 
lated demonstrates that in the Uredinales a generation of uninucleate 
cells alternates with a generation of binucleate ones, the binucleate 
series arising by the fusion of two uninucleate cells, and the nuclear 
fusion which occurs universally in the mature teleutospore being 
followed in the promycelium by what is with reasonable certainty a 
numerical reduction of the chromosomes. Proof of conjugate divi- 
sions in the hyphae and in spore formation is undoubted. The positive 
results obtained have stimulated research on species in other orders 
of the Basidiomycetes. Comparatively little is known, however, of 
the closely related group, the Auriculariales. 
Istvanffi (24) describes the germination of the basidiospores in 
Auricularia Samhucina, and figures a single spore transversely septate 
into two uninucleate cells, each giving rise to a cluster of curved, 
uninucleate conidia. He gives no other figures, and makes no further 
contribution to the cytology of the group. 
Sappin-Trouffy (48), working with Auricularia auricula-judae, 
traces the nuclear history from the young basidium to the mature 
spore. He states that the fruit-body is composed of interwoven hyphae 
possessing frequent transverse septa, the cells, in many cases at least, 
being binucleate. He makes no effort to determine the point of origin 
of this binucleate condition, and fails to state definitely whether 
multinucleate or uninucleate cells occur. The basidia arise as termi- 
nal cells on the peripheral hyphae of the sporophore, and in the young 
condition are binucleate. The two nuclei in the basidium later fuse, 
