STEVENS: PREVALENCE OF ENDOTHIA GYROSA 129 
of this fungus have not yet been discovered. The following notes 
indicate certain factors which seem to influence its prevalence 
within its present range. In discussing this question observations 
are confined to the eastern half of the United States, where most 
of the collecting was done and where, consequently, the distribu- 
tion of the species is fairly accurately known. This area is par- 
ticularly favorable for a study of the climatic relations of fungi 
since, as Ward (11) has pointed out, it constitutes a single climatic 
subdivision of the country. 
INOCULATION EXPERIMENTS 
In connection with work already reported (10), inoculations of 
E. gyrosa, E. fluens and E. fluens mississippiensis were made at 
various points from Charlottesville, Virginia, to Concord, New 
Hampshire, in the hope that data might be obtained concerning 
the effect of climate on their growth. The inoculations were 
located at points chosen for their availability and their nearness 
to United States Weather Bureau Stations. These places were 
visited every five or six weeks during the summer of 1914, twice 
during the summer of 1915, and once in May, 1916. At each 
visit ten or more new inoculations were made on species of Quercus 
(sometimes also on Fagus) using the method described for previous 
work (8, 10), and notes were made on the condition of the earlier 
inoculations. TABLE I gives a brief summary of the results of 
the observations on EF. gyrosa. 
The results of these inoculations have emphasized four facts, 
already known. Black oaks (Erythrobalanus Spach.) are much 
more favorable for the growth of E. gyrosa than white oaks 
(Lepidobalanus Endl.). E. gyrosa will under certain conditions 
grow and winter over as well near or beyond the northeast limits 
of its known range as it will within the region where it is most 
abundant. Water supply is important in the growth of the 
fungus. The condition of the host is important; this may be, at 
least in part, only another indication of the importance of the 
water supply, as obviously the water necessary for growth may be 
supplied by the host or by the atmosphere. 
An examination of the table shows that Endothia gyrosa sur- 
vived the winters of 1914-1915 and 1915-1916 without apparent 
