1922] WILLAMAN & SANDSTROM—SCLEROTINIA 289 
instances are known where the reaction of the sap is a controlling 
factor in a fungus disease. In the case of Sclerotinia cinerea no 
measurements have been made of its relation to the Px value of 
the medium, except some rough titrations made by Coo.ry (19) 
on cherry juice, which showed that this fungus can grow and sporu- 
late through a considerable range of acidity and alkalinity. 
Many investigators have sought for the mechanism by which 
fungi penetrate through the tissues of the host plant. Without 
going into the voluminous literature on this subject, it may be 
said that several different ways have been found: (1) by mech- 
anical pressure, (2) by enzymes which dissolve either the cell 
walls or the middle lamellae (12, 13, 19, 46, 53, 54), and (3) by toxic 
substances other than enzymes, especially oxalic acid (6, 7, 9, 12, 
13, 19, 42, 46, 53, 54). CooLry found oxalic acid produced by 
S. cinerea in small amounts, and VALLEAU demonstrated that 
solutions of this acid would disintegrate tissues, probably by 
removal of calcium from the pectic material of the middle lamella. 
The changes in composition which tissues undergo when rotted 
by organisms, and the differences in composition between resistant 
and susceptible varieties, have received considerable attention. 
One of the earliest of such studies was by BEHRENS (4), who used a 
number of fungi, among them Sclerotinia fructigena, on apple. 
REED (39) found that Glomerella not only decreases the acidity of 
apples and of synthetic media, but actually makes the latter alka- 
ine. HAwkins (28) found that Glomerella cingulata grown on 
peaches could hydrolyze and assimilate the pentosans, as well as 
utilize the monosaccharides, but that S. cinerea could not utilize the 
pentosans of the peach (29). In the latter case there was an 
increase ‘in titratable acidity during the rotting. In the case of 
potato tubers infected with various species of Fusarium (31) there 
was a decrease in sucrose, reducing sugars, pentosans, galactans, 
and dry matter; an increase in crude fiber, due to its formation in 
the hyphae of the fungi; and no change in the starch and methyl 
pentosans. Bispy (6) and Epson (21) also reported no effect on 
the starch of potato tubers by certain fungi, and suggest that 
potato starch could be made from rotted tubers. VALLEAU (46) 
examined many plum varieties as to their content of tannin, but 
