320 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 10 



niger was proportional to the amount of nitrate and also to the 

 concentration of the sugar of the culture medium. 



The action of nitrate on lower organisms was studied by 

 Bottger ('21). Toxicity appeared at a certain concentration of 

 the nitrate, above which it became increasingly inhibitive until 

 the organisms were killed. The initial point of toxicity varied 

 with the other components of the nutrient. The different 

 functions, such as growth, enzymatic activity, and sporulation, 

 exhibited toxic response at different concentrations of the nitrate. 

 The specific nature of the toxic property was not determined, but 

 it was thought to be nutritive as well as physical (osmosis) . All 

 nitrates were found toxic regardless of the cation. Waterman 

 ('18) gave a series of tables indicating the influence of KNOi 

 on the rapidity of growth of Aspergillus glaucus. Kossowicz 

 ('12) demonstrated the poisonous effect of CaCN 2 on 10 different 

 fungi. 



Self-poisoning of fungi might be briefly mentioned here, as 

 the process is closely related to N metabolism. Uhlenhaut ('11) 

 grew species of Mucor on media containing the glucoside, amyg- 

 dalin, and found that growth was soon inhibited. This inhibition 

 was ascribed to the accumulation of benzene cyanhydrine which 

 imparted an easily recognizable odor to the solution. Where 

 fungi capable of utilizing cyanhydrine were cultivated with 

 Mucor, the latter made a much more abundant growth than in 

 pure culture. Amygdalin was little used in the presence of 

 other C sources. Wehmer ('13) noted self-poisoning of Penicil- 

 lium variabile on media with (NH^SO, as the N source. Boas 

 ('19), in a former article, had shown that a Cladosporium in media 

 having urea as the N source produced such large quantities of 

 NH, that the fungus was soon killed; amines, produced proteo- 

 lytically, were also thought to be instrumental in the death of the 

 fungus. Aspergillus niger, on a solution containing 2 per cent 

 urea, 5 per cent maltose, and the usual mineral salts, quickly 

 changed the reaction of the medium to strongly alkaline (P H 7.5- 

 8.3). A strong odor of ammonia and amines was evident, the 

 NH, neutralizing the oxalic acid produced from the sugar. The 

 fungus was killed in from 7 to 9 days on this medium, as it was 

 also on that containing various amounts of maltose, dextrose nlus 



