2 82 ON A NEW CANKER DISEASE OF PRUNUS YEDOENSIS, etc. 
means the grades of hyphal growth. The — sign indicates the negative results. 
Per cent, 
of 
tannic acid 
The causal fungus 
Valsa Mali 
Valsa Paulowniae 
Growth 
Remarks 
Growth 
Remarks 
Growth 
Remarks 
No tannin 
+ + 
+ + 
+ + 
O.I 
+ + + 
+ + + 
Hyphal growth 
most vigorous 
+ + 
0.2 
+ + + 
Pycnos pores 
produced 
1 Hyphal growth 
most vigorous 
+ 
O.4 
+ + + + 
Hyphal growth 
most vigorous 
+ + 
+ C-) 
O.8 
+ + + 
+ C-) 
-(+) 
Fungus growth 
in a few tubes 
Fungus growth 
in a few tubes 
1.2 
+ 
—( + •) ] *" un g us growth 
1 in a few tubes 
2.0 
+C-) 
-C+; 
Fungus growth 
in a few tubes 
- 
5° 
-C+) 
Fungus growth 
in a few tubes 
8.0 
I 
II.O 
I4.O 
As already stated, the stromata and the pyenospores of the causal fungus 
were formed not only on the bark-decoction-agar, but also on the oat agar. 
It is, therefore, not by the tannic acid alone that the spore production is 
induced. On the fruit decoction, the hyphal growth is very vigorous, but 
the spores are not developed. Valsa Paulowniae, however, readily produces 
numerous pyenospores on the apricot-juice-agar. From these facts, one 
may see the importance of the knowledge of the effects of a certain acid on 
the fungi under consideration. For the purpose of determining this question, 
I added the 0.2, 0.4, 0.8, 1.2, 2.0% of citric acid, to the same standard 
medium employed in the previous experiments, and on which I have cultured 
the three species of Valsa using the same methods and placed under the 
same conditions. In this series of experiments I got comparatively good 
results relating to both the spore production and the hyphal growth. Accord- 
ing to my test by titrating with a certain solution of NaOH, using Phenol- 
phthalein as an indicator, the acidities of solutions of citric acid are very 
much higher than those of the same per cent solution of tannic acid. 
