FIXATION OF NITROGEN BY FUNGI 



185 



Some of them report a considerable gain of nitrogen without 

 any initial nitrogen furnished, wliich would imply a vigorous 

 growth, although that point is seldom mentioned by any of 

 them. Some, as Dox, mention the fact that there was no growth 

 beyond germination. 



It seemed that any further precaution in the way of controls 

 and the exclusion of combined nitrogen from the atmosphere 



TABLE 3 



Experiment B. Aspergillus in Czapek's solution with 5% dextrose. In other re- 

 spects the same as Experiment A, viz., 5 cc. of solution + 1 cc. or 2 cc. of ammonia 

 solution per culture, making 6 cc. and 7 cc. respectively 



Czapek's solution is made up as follows: K2HSO4 1.00 gm., MgS04 0.50 gm., 

 KCl 0.50 gm., FeS04 trace, water (dist.) 1000.00 cc. 



TABLE 4 



Experiment C. Aspergillus cultures in Czapek's solution with 5% dextrose. 5 cc. 

 per culture -f 1 cc. or 2 cc. of ammonia solution added, making 6 cc. or 7 cc. re- 

 spectively, per tube 



was unnecessary until there should be found some indication 

 of a gain in nitrogen over that furnished at the outset, which 

 had been measured with the greatest possible accuracy and 

 without any apparent loophole or cause for doubt. In other 

 words it was considered that it would be soon enough to look 

 for the sources of fixation or gain and the relation to dry weight 

 carbohydrate economy, etc., after some fixation or gain had been 

 demonstrated and not before that. 



Accordingly, cultures were continued as before, varying the 



