ON A NEW CANKER-DISEASE OF PRUNUS VEDOENSIS, etc. 
Table II. 
Table showing the effect of the different percentages of citric acid in the 
standard medium on the development of the causal fungus and tivo other species 
of Valsa. 
Per cent, 
of 
citric acid 
The causal fungus 
VaLsa Mali 
Valsa Paulowniae 
Growth 
Remarks 
Growth 
Remarks 
Growth 
Remarks 
No acid 
+ 
+ 
+ 
0.2 
+ + 
+ 
+ + + + 
Hyphal growth 
most vigorous 
0.4 
+ + 
Pycnospores 
produced 
+ 
1 Hyphal growth 
+ "*" 1 most vigorous 
O.8 
Hyphal growth 
most vigorous 
+ + 
Hyphal growth 
most vigorous 
Pycnospores 
produced 
1.2 
+ + 1 
_j_ ^_ I Pycnospores 
produced 
, * Some of cultures 
■° +{ - ' ! turn to black 
+ (-) 
, 1 Pycnospores 
1 p roduced 
Experiment II. 
The next experiment was made with only the cultures of the causal 
fungus, using the standard medium of corn-meal-agar to which had been 
added the following percentages of tannic acid : o. 1 , 0.4, 0.7, 1 .0. To make 
the standard medium I used the following method : — 
1 5 grams agar melted in 500 c. c. water. 
1 5 grams corn meal cooked in 500 c. c. water for one hour. 
Strain through cloth. 
Mix the two and filter through cotton. 
In this experiment, I used Erlenmeyer's flasks containing 25 c. c. of the 
media in each. The cultures were started on the 23rd of December, 191 4. 
The observations were continued to April, 1915, and the following results 
were obtained. 
( 1 ) The growth of the fungus causes no darkening of the check-medium 
containing no tannic acid ; but when tannic acid is added, even as low as o. 1 °j 0 , 
the growth of the fungus causes a darkening of the medium, as ah ead}' stated 
in the case of the first experiment. 
