CYTOLOGY OF EOCRONARTIUM MUSCICOLA 
in which the basidia are formed without clamps (Levine, 33). More- 
over, it fails to explain how the binucleate condition arises in species 
lacking clamp connections. He promises to elucidate these latter cases 
in a further contribution. 
It is difhcult to apply Kniep's explanation of the origin of the 
binucleate condition to Eocronartium muscicola. If clamp connec- 
tions occur in this species for a brief period following spore germina- 
tion, it does not seem logical to suppose that they would function as 
described by Kniep for a few cell generations and then cease to be 
developed on all the older mycelium. It seems probable to the writer 
therefore that clamp connections are wholly absent in Eocronartium 
muscicola. 
Since the binucleate series in the Uredinales is initiated by a simple 
cell fusion, the discovery of a similar phenomenon in members of the 
Auriculariales would not be unexpected. Possibly such a fusion oc- 
curs in Eocronartium muscicola at a point in the life cycle following 
soon after spore germination. Since many facts in connection with 
this fungus indicate its close relationship with the rust fungi, this is a 
reasonable hypothesis. The investigation of the cytology of other 
members of the Auriculariales is very desirable in this connection. 
It is possible that other species present more favorable material for the 
determination of the origin of the binucleate condition than is available 
in Eocronartium muscicola. The determination of this point is of 
unusual interest because of its bearing on the phylogeny of the Uredi- 
nales. 
Summary 
1. The investigation of the cytology of Eocronartium muscicola 
is based on material from a single host, Climacium americanum, 
collected in the vicinity of Ithaca, N. Y. 
2. The mycelium of the parasite is intracellular and permeates 
throughout the host plant from the underground stolons to the tips 
of the erect gametophoric branches. All the cells of the mycelium in 
which the nuclear number has been determined are binucleate, and 
conjugate divisions occur regularly. Uninucleate or multinucleate 
cells have not been found. 
3. The fungous sporophore arises at the tip of a gametophoric 
branch of the moss plant, and is formed by the outward growth of the 
endophytic hyphae. These hyphae pass out into the spaces between 
