Charles B. Lipman 



177 



TABLE II. 



A glance at Table II shows the influence of the kind of medium 

 on the amount of nitrogen fixed. Not only does dextrose allow 

 of a much larger fixation of nitrogen by the same organisms which 

 showed fixation in mannite solutions but it allows other organisms 

 to fix nitrogen which showed but a small nitrogen fixing power 

 or none at all in the other medium. This is a factor which can- 

 not be overlooked in considering the practical phases of nitrogen 

 fixation as related to the nitrogen supply for plants in the uni- 

 verse. Here again, it would appear, the pseudo yeasts are more 

 efficient at nitrogen fixation, when showing that power at all, 

 than the true yeasts. For Aspergillus niger we find dextrose to 

 be far superior to mannite as a source of energy, and we find it 

 to have a power of nitrogen fixation in the medium which corre- 

 sponds closely to that exhibited by the same organism in the hands 

 of other investigators above mentioned. Penicillium glaucum, 

 too, manifests a definite power of nitrogen fixation in dextrose 

 solutions and this again corresponds to the results obtained by 

 other investigators whose work is above reviewed. 



We find thus that at least eleven of the fifteen organisms above 

 tested show more or less pronounced powers of fixing nitrogen. 

 Owing to the higher content of nitrogen in the tap water used at 

 this time and also the higher content of nitrogen in the lye and 



