FIXATION OF NITROGEN BY FUNGI 



183 



HCl and NaOH, the results of which agreed with the theoretical 

 values. 



This solution, prepared and standardized with the highest 

 degree of care and accuracy, was pipetted into the separate 

 culture-tubes by means of a special Ostwald pipette. 



These culture solutions, thus prepared, were then sterilized 

 in the autoclave at 15 to 17 lbs. pressure for 20 minutes and 

 when cool they were inoculated with spores from newly grown 

 Aspergillus niger and incubated at 28 to 30°C. for varying 

 lengths of time, as shown in the tables, from 12 to 30 days. 



TABLE 2 



Experiment A. Aspergillus and Penicillium cultures in Saida's solution ivith 

 5% cane sugar and nitrogen as (NHi)2S0i added. 1 cc. and 2 cc, respectively, 

 added to 5 cc. of solution = 6 and 7 



* The cultures of Penicillium gave the same results as Aspergillus. Both 

 produced a good growth and abundant spores when nitrogen was furnished but 

 when not furnished merely germinated and produced no further growth that 

 could be called normal. The Penicillium was abandoned after this experiment. 

 Saida's solution is made up as follows: K2HPO4 0.4 gm., MgS04 0.4 gm., CaCU 

 trace, water 100.0 cc. 



As con.trols, a set of similarly prepared solutions were inoculated 

 just previous to sterilization and kept after sterilization, with 

 the dead spores, alongside the other tubes throughout the 

 remainder of the experiment and analyzed at the same time as 

 the others. This was afterwards found to be unnecessary as 

 the spores contained only a negligible amount of nitrogen and 

 this method was abandoned for another simpler one. 



It was agreed that the taking up of nitrogen from the air is 

 simply a matter of absorption, governed by the laws of diffusion 

 and since this is dependent solely on the amount of absorption 

 surface presented by the culture, blanks of water only would 

 serve the same purpose, cost less trouble to prepare, and be 



