DEPARTMENT OF BOTANICAL RESEARCH. 65 



In every instance except one (a species of Fusarium) the maximum 

 yield was in the combination of glucose and peptone as sources of 

 carbon and nitrogen, respectively. The organism which gave the 

 highest growth-quantity in this medium was Botrytis cinerea. On 

 the other hand, peptone as a source of both carbon and nitrogen gave 

 the lowest yield in every instance except one, which fact is significant, 

 and the work is being developed in this direction. Comparing potas- 

 sium nitrate and ammonium nitrate as sources of nitrogen, the ad- 

 vantage is more frequently with potassium nitrate, though there are 

 some peculiar and striking adjustments which may not be specifically 

 discussed here. It appears, too, that these relations are more or 

 less influenced by temperature and by the concentration of the 

 nutrients. 



Another phase of the work upon which investigation has been well 

 initiated is the influence of commercial vitamin products on the car- 

 bon and nitrogen metabolism of these organisms. The experiments 

 now in progress are to determine, first of all, whether the vitamins 

 supplied are in any way important in the nutrition of these organisms. 



Effects of Certain Sources of Carbon and Nitrogen on the Production of Acid 



by Fungi, by B. M. Duggar. 



After the growth of the organisms in the cultures referred to in the 

 previous section, the H-ion concentration of the remaining culture 

 media, (the filtrates from the fungus mats) was examined colorimetri- 

 cally with a view to the utilization of such data in pointing out, if 

 nothing more, at least the direction of metabolism in respect to acidity 

 or alkalinity of the bj^-products. 



^^Tien peptone alone served as a source of both carbon and nitrogen, 

 the H-ion concentration was shifted (by every organism except Asper- 

 gillus niger) toward alkalinity and generally beyond the neutral point. 

 When peptone and glucose were combined, 8 organisms increased the 

 acidity of the medium, 5 developed an alkaline reaction, and the re- 

 mainder produced very slight, if any, change. With potassium nitrate 

 and glucose, all the organisms used shifted the reaction in the direction 

 of alkalinity at a temperature of 58° to 61° F. except Aspergillus niger 

 and Botrytis cinerea. With ammonium nitrate as a source of nitrogen, 

 11 organisms produced a change towards alkalinity and 6 toward 

 greater acidity. 



It is notable that such diversity as referred to above exists in the 

 cultures of these organisms, and the problems involved are doubtless 

 complex. Changes in hydrogen-ion concentration may or may not be 

 significant, and it is early to make any specific assumptions, much less 

 to deduce any general rules; but it is certain that the relative concentra- 

 tion of nitrogen and carbon sources, partial exhaustion of the media, 

 temperature, and other factors are important in determining the reac- 

 tion of the medium. 



