[Vor. 1 
318 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
the fruit being market ripe on August 19. In these tests my 
results agree with those obtained by Bigelow and Gore (10) 
for peaches, and with those of Thompson and Whittier (49) 
for some other fruits. Тһе last mentioned investigators, how- 
ever, found that the acidity of peaches decreases toward matu- 
rity. I have been unable to secure data covering the acidity of 
plums throughout the season. 
The above results show that the acid content of plums in- 
creases rather than diminishes toward the maturity of the fruit. 
The results of the experiments and field observations show that 
mature and ripe fruit is much more susceptible than the green 
and immature fruit. Тһе above facts, showing that as the fruit 
approaches maturity the acidity increases while the suscepti- 
bility to the disease also increases, indicate that there is no 
close relationship between the low acid content of the host and 
susceptibility to the brown-rot fungus, and that we must look 
to other factors to explain infection as observed in the field. 
Ав pointed out, my experiments indicate that penetration is a 
TABLE III 
RELATION OF THE GROWTH OF SCLEROTINIA CINEREA TO THE REACTION OF 
THE MEDIUM 
Meum | Acidity | Orb after | Growth atter | Spe 
Cherry juice | +2.3* -1 +t + 
Cherry juice | +1.5 ++ ++ ++ 
Cherry juice | +1.0 +++ ++ ++ 
Cherry juice | +0.15 - + + 
Cherry juice | —0.15 | 0 ++ 0 
Cherry juice | | —0.30 0 ++ 0 
*Acidity is given in ec. of N/10 NaOH necessary to neutralize 1 cc. of the juice. 
{The + sign indicates a fairly good mycelial growth, or spore formation, and the 
— sign indicates that the growth was just perceptible; 0 indicates no growth, or no 
spore formation. 
— 
