Nov. 29, 1915 
Varietal Resistance of Plums to Brown-Rot 
385 
was still firm in the center. After 48 hours it had softened completely. 
A portion not immersed in the liquid, but which came in contact with it 
at one point, was softening from this point and becoming discolored. 
The checks in water remained firm and were not discolored. 
Although the effect of the extract on the apple tissue appeared to be 
that of a pectinase, it can hardly be concluded that this enzym was 
present, as the fruit used was overripe and slightly mealy, and could very 
easily have been broken down by other solvents contained in the extract. 
DeBary (1886) considered the possibility of oxalic acid being the toxic 
substance produced by S. lihertiana , because he found the hyphae often 
coated with crystals of it; however, he later discarded this notion for 
the reason that solutions of oxalic acid did not give the same effect as the 
fungus. Smith (1902) extracted a substance from Botrytis cinerea , 
which, whether boiled or unboiled, caused a rot of the host tissue iden¬ 
tical with that caused by the fungus. He concluded it was not an 
enzym, but that the effect might be due to oxalic acid, which he found to 
be present in quantities often as high as 2 per cent. Peltier (1912) con¬ 
firmed the results regarding this action of the extract, but was unable to 
detect the presence of oxalic acid, even in old cultures. 
The possibility of oxalic acid being the toxic substance of 5 . cinerea 
was considered, as Cooley has demonstrated that it is produced in appre¬ 
ciable amounts in cultures of S. cinerea on plum and peach juice, and 
in peaches which had been rotted by the fungus. In order to determine 
the effect of oxalic acid on vegetable tissue, small blocks of onion, potato, 
tomato, dahlia, radish, coleus (young shoot), tomatoes (young shoot), 
loquat (fruit), canna (bulb), oxalis (petiole), geranium (young shoot), 
and apple were immersed in 0.015, 0.062, 0.125 P er cent solutions of 
oxalic acid and the effect noted at the end of 24 and 48 hours. In all of 
the solutions the apple, loquat, and oxalis softened, while in the 0.125 
per cent solution only the onion and tomato softened slightly. The 
potato did not soften even in 0.25 per cent solution. In all cases bleach¬ 
ing occurred. An examination of the different tissues showed that the 
softening was due to the solution of the middle lamella. 
The fact that oxalic acid even in such dilute solutions readily softened 
the tissues^of the apple and loquat, upon both of which the brown-rot 
grows readily, might indicate that the oxalic acid was the toxic sub¬ 
stance, but the bleaching effect produced by the acid and the fact that 
when used even as strong as 0.25 per cent it had no effect on potato, upon 
which the fungus also grows readily, would seem to indicate that this acid 
is not the sole toxic substance produced. 
COMPARISON OF FIRM-ROT AND SOFT-ROT 
Cooley (1914) pointed out the very interesting fact that, although 
P. expansum and 5 . cinerea apparently acted differently on their hosts, 
the one producing a soft-rot of fruits and the other a firm-rot, in culture 
