May 16, 1921 Glucose as a Source of Carbon for Storage-Rot Fungi 207 
to 12.52, 19.04, and 9.31, respectively. In the first and last cases the 
osmotic pressure is reduced, the latter more than the former, but in neither 
case in proportion to the amount of sugar actually disposed of. In 
M. racemosus , which reduced the sugar by nearly one-half, the osmotic 
pressure was actually increased. A study of the two tables will show 
other similar results. These facts may be explained in part by assuming 
that some of the sugar was broken down into some substance or sub¬ 
stances which held the osmotic concentration up to, or in some cases 
raised it above, that of the control. 
CHARACTER OE MYCELIAL, GROWTH 
The fungi all looked very much alike when grown upon the culture 
medium without glucose present. The mycelium was white or grayish 
in color, very fine, and usually formed a thin felt over the surface with 
a small amount of submerged threads. Except in Rhizopus tritici y 
no sporulation took place, and then only an occasional sporangium was 
formed. With two exceptions, all the fungi studied made a fairly good 
growth in concentrations of glucose varying roughly from 10 to 40 per 
cent. Sphaeronema apparently is not able to utilize glucose, since 
in no case was the growth perceptibly increased by its presence. Of 
the eight fungi, Penicillium alone was able to grow in the strongest 
concentration. Diplodia tubericola , R. nigricans , Mucor racemosus , 
and Sclerotium bataticola made some growth in all but series VII, while 
Fusarium acuminatum made a sparse growth in series VI. Sphaeronema 
fimbriatum and Botrytis cinerea failed to thrive in series V and VI, re¬ 
spectively. Although Penicillium grew at the highest concentration 
used, it did not develop normally. No doubt this strength of dextrose 
represents approximately the limit of growth of this organism. 
SUMMARY 
(1) Eight fungi— Fusarium acuminatum , Diplodia tubericola , Rhizopus 
tritici } Mucor racemosus , Sclerotium bataticola, Penicillium sp., Botrytis 
cinerea , and Sphaeronema fimbriatum —which cause decay of sweet 
potatoes in storage, were grown at a constant temperature of 28° C. 
on a modification of Czapek’s nutrient solution, with different amounts of 
glucose as a source of carbon. All these fungi except S. fimbriatum 
utilized glucose in considerable amounts. 
(2) The different fungi varied greatly in the amount of glucose they 
actually consumed at the same concentration. In general, the greatest 
consumption was in the weaker solution (10 per cent) and decreased 
progressively with the increase of the concentration. With two ex¬ 
ceptions, all the organisms grew in solutions containing from 42 to 50 
per cent glucose. Penicillium sp. alone grew in a 58 per cent solution. 
(3) A great variation was found among the different fungi in the 
amount of dry material that was produced at the same concentration. 
