Heald: Chestnut Blight Fungus 
277 
nies does not appear to be of importance since this varies accord- 
ing to crowding, depth of medium and origin. The reliability of 
this method for differentiating pycnospore and ascospore colonies 
has been substantiated by numerous cultures, but the importance 
of holding the cultures at a constant temperature must not be 
overlooked. 
Forest Pathology Laboratory, 
United States Department of Agriculture, 
Philadelphia, Penna. 
Explanation of Plates 
Plate XCVIII 
Germination of pycnospores in 3 per cent, dextrose agar, plus 10, at 22° C: 
I, after 12 hours; 2, after 16 hours; 3, after 22 hours; 4, s, 6, after 36 hours. 
These illustrate the linear and the Y-types of germination. 
Plate XCIX 
Germination of ascospores in 3 per cent, dextrose agar, plus 10, at 22° C. 
1-4, a series showing stages in the growth from a single spore: i, at 11:45 
A.M. ; 2, at 2:45 P.M. ; 3, at 4:45 P.M. ; 4, at 7:45 P.M. ; 5, 6, 7, after 24 
hours. In 4 each cell has produced two hyphae ; in 5 one cell has produced 
two hyphae, while a strong lateral has grown out from the main axis just 
beyond the other cell of the spore ; in 6 one cell has produced a short lateral 
but no terminal hypha ; in 7 one cell of the ascospore failed to produce a 
germ tube. 
Plate C 
A series of drawings showing the comparative growth from an ascospore 
and a pycnospore in 3 per cent, dextrose agar, plus 10, at a temperature of 
25° C. After eight hours drawings were made at hourly intervals for the 
ascospore series and every two hours for the pycnospore series. 
Plate CI 
Poured plate cultures of ascospores and pycnospores to show comparative 
growth in 3 per cent, dextrose agar, plus 10, at a temperature of 25° C. Pho- 
tograph taken after three days of growth. Pycnospore colonies not yet visible 
to the naked eye. 
