1914] 
COOLEY—SCLEROTINIA CINEREA 319 
very important factor. It is possible that a study of the tannin 
content' might yield some relation of interest. 
A preliminary experiment was planned to determine the 
acidity at which the optimum growth and spore production of 
the fungus occurs. For this purpose the juice from ripe sour 
cherries was used. The juice was squeezed out of the cherries 
(no water being added) and a portion titrated to determine the 
acidity. Then 50 cc. of this liquid were put into each of a 
number of Erlenmeyer flasks of 125 cc. capacity; some of the 
flasks were left untreated, while others received various quanti- 
ties of N/10 NaOH to bring each to the desired acidity or alka- 
linity. Тһе flasks were then sterilized and inoculated. Тһе 
results are given in table rrr. 
It is clear, therefore, that although the fungus eventually 
grows on а medium as acid as the natural juice of sour cherries, 
it grows more luxuriantly on a somewhat less acid medium. 1% 
is à rather significant fact that on the media near the neutral 
line the fungus at first shows no perceptible growth, but at the 
expiration of two weeks has produced nearly as much mycelial 
growth as on the acid medium. It is also of interest to note 
that we find spore formation abundant on the very acid media 
but entirely lacking on the alkaline media. This experiment 
indicates that the fungus can adjust itself to a slight degree of 
alkalinity. 
OXALIC ACID PRODUCTION BY THE FUNGUS 
The first important reference to охаПе acid production by 
fungi is in the publication by de Bary reviewed in a preceding 
section. He reports that the older hyphe of the fungus were 
encrusted with crystals of oxalic acid, and he attributed some 
of the poisonous action of the parasite to the production of this 
substance; in fact, he mentions oxalie acid fermentation. Since 
the appearance of de Bary's paper a limited number of investi- 
! Cook and Bassett and their associates (17) believe that there are enzymes in the 
host plant which may act upon cell constituents and play the réle of alexins. They 
are of the opinion that tannin, as such, is not abundant in fruits, but that it may be 
formed by the action of oxidizing enzymes upon certain phenols. Injuries produced 
by parasitic fungi may accelerate the activity of the host in the production of tannin, 
the latter perhaps being toxic to the growth of parasitic fungi. 
