[Vor. 1 
166 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
the marked fixation of free atmospheric nitrogen it is impossible 
to say, the author states. However, from his own results, and 
those of previous investigators, that the presence of algee exer- 
cises а favorable effect on the process of free-nitrogen fixation, 
and, further, that the alge thus far studied in pure culture do 
not possess this faculty of fixation, Kossowitsch concludes that 
the alge play an indirect róle. Не believes they do this by 
furnishing, through their photosynthetic activity, carbohydrates 
to the nitrogen-assimilating bacteria. He would look upon the 
alg: as occupying the same position with reference to free-living, 
nitrogen-fixing bacteria as the legumes do with reference to the 
nodule organisms. 
Stocklasa (35), while not making his conclusion very clear, 
leads one to believe that he considers certain algæ (which he 
fails to enumerate) capable of fixing free atmospheric nitrogen. 
Unfortunately, all of Stocklasa’s experiments were carried out 
with impure cultures. Molisch (23), in conducting experiments 
with alge relative to the necessary nutrient elements, attempted 
to cultivate Microthamnion Kiitzingianum Näg., Stichococcus 
bacillaris Nàg., S. major Rbh., Ulothrix subtilis (?) Kütz., and 
Protococcus sp.—all in impure culture—on a nitrogen-free 
mineral nutrient solution. In every case the alge failed to grow, 
and Molisch was led to the conclusion that alge require com- 
bined nitrogen for their development. Although no ехрегі- 
ments in which combined nitrogen was furnished to the algee 
were conducted, the author nevertheless makes the statement, 
based principally on the work of Kossowitsch just reviewed, that 
algee are not able to fix free atmospheric nitrogen. 
In the next year Bouilhac (4) reported that he had succeeded 
in isolating in pure culture Schizothrix lardacea, Ulothrix flaccida, 
and Nostoc punctiforme. "Unfortunately, this author does not 
give a detailed account. of his isolation methods. Six flasks 
containing а mineral nutrient solution free from combined 
nitrogen were inoculated with each alga, and to three of each a 
drop of soil suspension was added. Хо growth whatever devel- 
oped in any of the Schizothriz and Ulothrix cultures, nor in the 
Nostoc cultures to which the suspension had not been added. 
But in those cultures of the latter to which a drop of soil suspen- 
sion had been added, a splendid growth appeared and in each 
