[VoL. 3 
418 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
experiments. Cultivated during a period of 28 days on 50 ce. 
of nutrient solution the 5 races of Phoma radicis gave a nitro- 
gen fixation ranging from 2.3 mg. in the lowest to 15.7 mg. in 
the highest. For Aspergillus niger and Penicillium glaucum 
the fixation was 1.9 and 2.8 mg., respectively. The usual high 
fixation was secured with Azotobacter chroococcum and Clos- 
tridium pastorianum. In spite of the fact that the methods 
employed are those generally recognized as unimpeachable, 
still attention should be drawn to the fact that in such cases 
as those of Aspergillus and Penicillium, where the fixation is 
only about 2 mg., the technique employed must be subjected 
to the closest scrutiny. It is noted that the felt was separated 
from the culture solution in the usual way, and further that 
the solution was then made up to the original volume (a pro- 
cedure of vital importance when aliquot parts of the solution 
serve for analysis, and one seldom mentioned). Then from 
one-sixteenth to one-fourth, depending upon the amount of 
sugar present, of the total solution was taken for the analysis. 
In this way any small experimental error involved would have 
been multiplied 4-16 times. 
Equally satisfactory in respect to method is the work of 
Froehlich (’08). Here again the methods are described in 
sufficient detail so that one is not left in doubt as to import- 
ant parts of the technique. The organisms used lend a par- 
ticular interest to the work, inasmuch as they were isolated 
from dead and decaying plant material and are fungi gener- 
ally considered important in the decay of vegetation. Those 
selected consist of one species from each of four common 
genera. All were found to fix nitrogen to a slight degree, 
averaging as follows: Alternaria 3.34, Macrosporium 3.70, 
Cladosporium 2.26, and Hormodendron 1.93 mg. Many sub- 
sidiary experiments of interest are included. 
Zikes (209) conducted extensive experiments to determine 
the free nitrogen relations of a yeast-like organism isolated 
from the leaves of laurel and called by him Torula Wiesneri, 
which he cultivated on flasks containing 300 ce. of culture 
fluid. He employed the Dumas method of analysis, filtered off 
the fluid from the yeast cells, and made separate determina- 
