Lewis Knudson 201 



10 per cent sugar the gallic acid, so far as my previous results'^ 

 show, is not at all absorbed from the nutrient solution. Why 

 the increase in gallic acid should increase the amount of tannase 

 produced is therefore difficult to explain. The writer is not pre- 

 pared at present to offer an explanation. 



VII. SUMMARY. 



1. There is a progressive increase of tannase in the two organ- 

 isms Aspergillus niger and Penicillium sp. with increased concen- 

 tration of tannic acid in Czapek's solution containing 10 per cent 

 sugar. 



2. In a full nutrient solution containing, as a source of carbon, 

 2 per cent tannic acid, the addition of cane sugar decreases the 

 quantity of the tannase produced by the organism. The higher 

 the concentration of sugar the lower the quantity of tannase pro- 

 duced. 



3. Aspergillus niger produces more tannase or a more active tan- 

 nase per unit weight than Penicillium sp. 



4. The production of tannase in Aspergillus niger, Penicillium 

 sp. and Penicillium rugulosum is stimulated by tannic acid and 

 gallic acid, only, and the former is more effective than the latter. 



5. There is a progressive increase of tannase in Aspergillus niger 

 with increased concentration of gallic acid in a nutrient solution 

 containing 10 per cent sugar. 



VIII. DISCUSSION. 



box" in his excellent paper makes the following statement: "There is 

 no evidence that enzymes not normally formed by the organism in demon- 

 strable quantities can be developed by special methods in nutrition. The 

 influence of adding a particular substance to the medium is, therefore, not 

 to develop an entirely new enzyme, but to stimulate the production of 

 an existing enzyme, which is normally formed under all conditions." In 

 the light of Dox's results it seems somewhat surprising that the enzyme 

 tannase should be formed only under special nutrition. It may be as Dox" 



'^ Loc. cit. 



33 A. W. Dox: The Intracellular Enzymes" of Penicillium and Aspergillus, 



loc. cit. 

 3< A. W. Dox: Enzyme Studies of Lower Fungi, Plant World, xv, pp. 40-43, 



1912. 



