230 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



(Vol. 10 



The work of Hemmi ('20) is a typical example of this latter 

 type of work. Using a basic medium containing sugar and work- 

 ing with a large number of species of Gloeosporium, he studied 

 the effect of the addition of varying amounts of organic acids. 

 His general conclusion was that small amounts of these acids 

 increased the growth of the fungi over that produced by the 

 sugar alone, and larger amounts inhibited growth. The acids 

 were added in the free state and no account taken of P H so that 

 the reasonable supposition would be that the depression of growth 

 at the higher concentrations of acid was due to an unfavorable 

 P H . Unless the hydrogen-ion concentration is taken into account 

 such studies give very uncertain results. The chief work of an 

 analytical nature, therefore, has been done by workers using either 

 Aspergillus niger or some of the fungi from the Penicillium group 

 (including the fungi classified under the genus Citromyces Wehmer) . 

 A number of earlier writers attempted to classify the products 

 resulting from the fermentation of citric acid, and their results 

 are outlined by Thiele ('11). From the results of these workers, 

 using such inocula as spoiled cheese, hay decoction, etc., we find 

 reported as fermentation products, butyric acid, acetic acid, 

 succinic acid, ethyl alcohol, hydrogen, carbon dioxide, water, 

 and carbonates. It is difficult to evaluate the results of the very 

 early workers where neither culture methods nor chemical methods 

 were well standardized, but the meager descriptions of the bulk 

 of these experiments would point to yeasts and bacteria rather 

 than true fungi as the organisms bringing about the fermentations. 

 Special interest attaches itself, however, to the reported produc- 

 tion of alcohols from citric acid, inasmuch as there was strong 

 evidence in the present work that under certain conditions some 

 of the fungi produced alcohols and acetic acid in the presence of 

 citric acid, and presumably from it. Fairly recently Fitz (78) 

 reported alcoholic products obtained from the " spontaneous 

 combustion" of calcium citrate. His tests gave isopropyl alcohol, 

 a weak reaction for ethyl alcohol, and an uncertain test for suc- 

 cinic acid. Here again we know nothing of the actual agent of 

 fermentation but it was probably bacterial. The difficulties in 

 testing for such substances have no doubt hindered the work and 

 affected the accuracy of the reports, for it is seldom that a botanist 



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