lOI 



In April, 1915, we published another work (2), confuting two 

 publications of Oes and Molliard on the same subject. 



Since that time five works have been published on assimilation 

 of atmospheric nitrogen, one of which is of very recent date. 

 These may be considered briefly. 



In 1914, Schramm (3), working with pure cultures of seven 

 species of algae in nutrient solutions lacking nitrogenous com- 

 pounds, found that they did not assimilate nitrogen from the 

 air. 



Moore and Webster (4) in 1920 cultivated unicellular green 

 algae in a solution free from nitrogenous compounds and ob- 

 served that they fixed nitrogen from the air, grew and formed 

 proteids. They obtained, however, a greater and more rapid 

 assimilation of free nitrogen by adding nitrogenous compounds 

 to the nutrient solution. 



A year later the same authors with Whitley (5) published 

 another work in which they confirmed and extended the results 

 already obtained, concluding that marine algae, like fresh water 

 algae, can fix elemental nitrogen from water and indirectly from 

 the air in sunlight, but not in darkness. The amount of nitrogen 

 fixed exceeds by many times the total combined nitrogen origin- 

 ally present in the water of the culture in the form of aminos, 

 nitrites, or nitrates. 



Moreover, the small initial amounts of nitrogen present in 

 these forms are not decreased during the life of the algae. It 

 thus follows that the only available source is the free nitrogen of 

 the atmosphere. 



Another work published in the same year is that of ^^"'ann (6), 

 in which an investigation similar to those considered above is 

 extended to other species of algae. The author cultivated seven 

 different species of filamentous green algae in pure sterile cultures 

 on an agar medium containing glucose and mineral substances 

 to which either ammonium nitrate or calcium nitrate was added. 

 The nitrogen which was assimilated was derived from the free 

 nitrogen of the atmosphere. The amount of this food assimilated 

 ranged from i to 12.5 mg., representing an increase in the total 

 nitrogen content of the culture flasks of from 4 to 54 per cent. 



Five other species of Chlorophyceae were grown on a medium 

 containing ammonium nitrate and calcium nitrate but without 

 glucose. Four of these assimilated very little nitrogen, so that 



