May 16,1921 Glucose as a Source of Carbon for Storage-Rot Fungi 203 
that the growth of Lenzites sepiaria (Wulf.) Fr., Forties roseus (Alb. and 
Schw.)Fr., Coniophora cerebella (Pers.) Schroter, and Merulius lachrymans 
(Jcq.) Fr. in synthetic and malt extract media was not inhibited until 
a high hydrogen-ion concentration was reached. The limiting P H value 
was found to be near 1.7. All the fungi responded in about the same 
way, although there were distinct variations between the different 
organisms. Growth appeared to be retarded when a P H value of about 
3.0 was reached. As the acidity increased beyond this point the growth 
became markedly less. 
Webb (29) found that in a culture solution consisting of inannite, phos¬ 
phoric acid, and sodium hydroxid successively increasing the hydrogen-ion 
concentrations from approximately neutral to P H 3.1 to 2.8 influenced 
favorably the germination of the spores of Aspergillus niger , Penicillium 
cyclopium Westl., Botrytis cinerea , Fusarium sp., and Lenzites sepiaria. 
The different organisms had a different range of hydrogen-ion concentra¬ 
tion, permitting the germination of the spores as follows: A. niger , P H 2.8 
to 8.8; P . cyclopium 2.8 to 10+ ; B. cinerea 2.8 to 7; Fusarium sp., 2.8 
to 10+ ; and L. sepiaria 2.8 to 7. 
At certain concentrations some of the organisms studied by the writers 
had little or no influence on the acidity of the substrate, while others 
rendered it much more acid. For example, Fusarium acuminatum , 
Sclerotium bataticola , and Sphaeronema fimbriatum can hardly be inter¬ 
preted as exercising any influence on the acidity of the solution within the 
limits of these experiments. With all three of these fungi the hydrogen- 
ion concentration in the control at the same concentrations is actually 
higher than the solution on which the fungus grew. The differences are 
slight and in some cases well within the limits of experimental error, so that 
in general there are no outstanding examples of increase or decrease in 
acidity of any one of these three fungi. On the other hand, the remaining 
five organisms all show a considerable increase in the hydrogen-ion con¬ 
centration in solutions of different strength. Rhizopus tritici f for example, 
increased the acidity of the substrate from P H *4.2 to 1.81 in a solution of 
30 per cent dextrose, when the maximum hydrogen-ion concentration 
was reached. In general, it may be said that the highest concentration 
was reached in solutions containing about 20 to 30 per cent glucose and 
that it decreased above and below these strengths. 
Just how nearly these results represent the limits of growth for these 
fungi is not definitely known. The greatest growth was made during the 
first week; thereafter it slowed up. Whether or not this was due to the 
increase of acidity in the solution or to other causes can not be answered 
at the present time. 
Preliminary experiments showed that if Rhizopus tritici is grown several 
times on the same solution after removal of the fungus felt it finally 
reaches a stage when growth no longer will take place. These experiments 
were made with Czapek’s modified nutrient solution with a 2 and 1 per 
