1909] STEVENS & HALL—VARIATION OF FUNGI £5 
SUMMARY OF CHEMICAL RELATIONS NOTED 
The most striking response to chemicals is in color, which so far 
as observed was invariably heightened by the presence of chemicals 
bearing carbon in available form, the form of available carbon 
varying for different fungi. Some fungi, possessing ability to digest 
starch, can utilize this as a source, while to others the carbon of 
starch is inaccessible. Special unknown chemicals in apple add vivid 
colors to fungi otherwise hyaline. Some chemicals also promote or 
inhibit spore formation. Some inhibit or promote growth of setae 
and some even alter the size, color, and septation of spores. MILBURN,‘ 
working under Kiess, has also noted pronounced effects of chemicals 
upon the color of fungi. The difference in color effects produced by 
different fungi under the same conditions, and with the same fungus 
under different conditions, is also noted by BEssEy.? No correlation 
is noted between rapidity of lineal growth and nutritive value of the 
medium. In many instances most rapid lineal growth occurred in 
what was surely the poorest medium. Very poor media suffice in 
many cases also for spore formation, while rich media often result in 
cessation of spore formation. 
Colletotrichum Lindemuthianum, sometimes with setae, often 
without, has long been of questionable generic position. The same is 
true of several other species of this genus. Alternaria Brassicae and 
Macrosporium Brassicae agree closely except as to presence or 
absence of catenulate spores.*: Variation of this kind is probably 
due to variation in chemical composition of the supporting medium, 
e. g., change in sugar content as ripening proceeds, acting in such way 
as to give the fungus the appearance of belonging to one genus 
when upon the green sugar-tree fruit, to another genus as the starch 
gives place to sugar as the fruit ripens. 
IV. Light relation 
The absence of material effect of light upon lineal growth with these 
species of fungi is shown in Table I. 
Ascochyta Chrysanthemi Stevens.—The growth is more floccose 
in darkness. 
Phyllosticta sp.—This fungus forms its pycnidia in beautiful con- 
tt A. Brassicae “hyphis brevibus conidiis 60-80 X 14-18 4, 6-8 eo ig 
M. Brassicae “hyphis obsoletis conidiis 50-60 X 12-14 #, 5-11 septatis.” 
