398 
HARRY M. FITZPATRICK 
A detailed account of its parasitism, life history, and morphology has 
already been given in the writer's previous paper (12), and the facts 
need not be repeated here. 
The present investigation of the cytology of the species is based on 
material taken from a single host, Climacium americanum Brid., all 
the collections having been made by the writer in the vicinity of 
Ithaca, N. Y. Climacium americanum is a large moss, and the fun- 
gous sporophores produced on its branches are larger than those 
developed on smaller species. They are consequently more favorable 
for study. The large size of the host, moreover, renders it especially 
suitable in connection with the staining of the endophytic mycelium. 
Fortunately the fungus has been collected more abundantly on this 
host than on any other. 
Under favorable weather conditions the young sporophores, which 
make their appearance at the tips of the gametophoric branches, 
undergo rapid elongation, and within a period of two weeks begin to 
bear basidia and form spores. If dry weather prevails their develop- 
ment is retarded, and material favorable for cytological examination 
is not easily procured in the field. Parasitized host plants were, 
therefore, collected in the early summer, and placed in the greenhouse 
under conditions favorable for growth. Abundant moisture was 
provided and normal fungous sporophores developed in great numbers. 
In this manner excellent material illustrating all stages in the develop- 
ment of the fruit-body and its hymenium was easily obtained. 
Sporophores intended for subsequent cytological study were 
removed from the host at varying intervals and given a preliminary 
microscopic examination before they were placed in the fixing solution. 
A brief examination of the individual sporophores under the lower 
powers of the microscope proves of considerable service in demon- 
strating the presence of spores. Their comparative abundance fur- 
nishes a criterion for the determination of the age of the basidia. 
Since basidia of practically all stages of development are commonly 
found together on a single sporophore, this preliminary examination 
gives, however, only an indication of the predominating stages present 
in the hymenium. Sporophores collected in the field at different 
times during the growing season were placed in the fixing solution and 
subsequently studied in comparison with those developed in the green- 
house. 
For study of the endophytic mycelium, diseased host plants were 
