18 BULLETIN 727, U. S. DEPARTMENT OF AGRICULTURE. 
PHYSIOLOGY. 
Only preliminary work was done on the physiological phases of the 
problem, and since, as a rule, the tests were not made in duplicate, 
only a brief summary of the results will be presented. 
NUTRITION. ! 
LN 
In studying the nutrition of the fungus, use was made of a standard 
nutrient solution containing molecular+8 ammonium nitrate, mo- 
lecular +20 potassium acid phosphate, molecular+50 magnesium 
sulphate, molecular + 1,000,000 iron chlorid, and about 5 per cent 
sucrose. By substitutions within this formula, the effect of the 
omission of an element was determined. The fungus was grown in 
parallel series with Aspergillus niger in flasks containing about 50 
c. c. of the medium. Dry-weight yields were used as criteria. 
Using the full nutrient solution, it was found that in 24 days © 
Colletotrichum produced only. about one-twentieth as much dry- 
weight yield as did Aspergillus in 15 days, but after a much longer 
interval the yield of Colletotrichum was almost as great. No sporu- 
lation of the latter was secured and it was evident that a liquid 
medium was not well adapted to the development of Colletotrichum. 
As a result of substitutions in the formula it was found that car- 
bon, nitrogen, potassium, and phosphorus were essential to the 
erowth of Colletotrichum, while magnesium was needed in only very 
minute quantities. Sulphur and iron were not needed in excess of 
the amounts present as possible impurities. Colletotrichum seems 
to be less sensitive to a lack of magnesium and sulphur than Asper- — 
gillus and more sensitive to a deficiency of potassium and phos- 
phorus. 
Substituting other carbohydrates for sucrose, so that an equal 
amount of carbon was present, it was found that Colletotrichum, 
unlike Aspergillus, uses cornstarch to exceptional advantage. The 
other carbon sources, listed in descending order of suitability, are 
inulin, maltose, dextrose and galactose, salicin, glycerol, and lactose. 
Sucrose should probably be ranked with the dextrose and galactose. 
For Aspergillus the order would be sucrose, inulin and maltose, dex- 
trose, cornstarch, galactose, tannin, glycerol, lactose, and salicin. 
Colletotrichum was unable to utilize tannin. 
Further proof of the preference of Colletotrichum for the more 
complex carbon compounds was afforded by its abundant develop- 
ment on xylan as a carbon source. Using xylan prepared from straw 
in place of sucrose in an amount such that only one-fourth as much 
carbon was available as in the full nutrient solution, a similar -dry- 
weight yield of fungus mycelium was obtained. Xylan appears to 
be fully as suitable a carbon source as cornstarch. 
1 The tests relative to nutrition and the effect of copper sulphate were made under, the direction. of Prof. 
J. B. Overton and Dr. J. P, Bennett, of the University of Wisconsin. 
