THE UTILIZATION OF CERTAIN PENTOSES 
377 
shown that the pentoses can be used by fungi, but it is generally 
agreed that they can not be fermented. 
In regard to the utilization of pentosans by fungi it seems probable 
from the work of Czapek^^ and Schorstein^^ that certain components 
of the cell walls of woody tissues are rendered soluble and utilized by 
some fungi. The last mentioned writer reaches the conclusion that 
xylan is digested by Merulius lachrymans. He bases his conclusion 
upon the observed difference in optical rotation of extracts of wood 
before and after it had been acted upon by the fungus. Swartz^^ 
found apparently that the pentosans of Rhodymenia palmata, a marine 
alga, were hydrolyzed to a reducing substance by "Taka diastase." 
Duggar and Davis^^ recently announced that they were unable to 
demonstrate the presence of a pentosanase in Fucus. 
It seems then that pentosans and pentoses are of some value as 
food for higher animals but that these organisms probably secrete no 
enzymes capable of hydrolyzing pentosans. Some of the invertebrates 
can utilize pentoses readily and seem to be able to hydrolyze some 
pentosans. Pentoses have been found to be a good source of carbon 
for certain fungi and there is evidence that some pentosans may be 
broken down through the action of enzymes secreted by fungi. The 
products of such enzyme action have apparently not been identified. 
It was to obtain more information upon the effect of parasitic 
fungi on pentoses and their compounds that the experiments described 
in this paper were planned and carried out. The study includes a 
series of experiments on the effect of Glomerella cin gulata (Stonem.) 
S. & V. S. upon pentose compounds in the apple fruit, a series on the 
utilization of pentoses and certain of their compounds as sources of 
carbon for this fungus, and experiments upon the effect of the extract 
of the fungus mycelium under aseptic conditions on xylan. 
The fungus was isolated from apples kindly furnished by Dr. C. 
L. Shear and was maintained in stock culture in tubes of cornmeal 
agar throughout the study. In the experiments on the effect of the 
fungus upon the pentose-containing compounds in apples practically 
1^ Czapek, F. Zur Biologic der holzbewohenden Pilze. Bericht. Deutsch. Bot. 
Ges. 17: 166-170. 1899. 
Schorstein, J. Zur Biochemie der Holzpilze. Centralbl. Bakter. und Parasit. 
Abt. II 9: 446-447. 1902. 
1^ Swartz, Mary Davies. Loc. cit. 
Duggar, B. M., and Davis, A. R. Enzyme Action in Fucus vesiculosus L. 
Ann. Mo. Bot. Gard. i: 419-426. 1914. 
