1914] 
SCHRAMM—GRASS-GREEN ALGJE AND ELEMENTARY NITROGEN 167 
culture analysis showed a nitrogen fixation of from 11 to 23 
milligrams. From a second series (in which the cultural solu- 
tion contained per liter 0.1 gram arsenic acid in the form of 
potassium arsenate) a similar result was obtained, with fixation 
of nitrogen of from 5 to 60 milligrams. Тһе presence of Ulo- 
thrix or Pleurococcus in addition to the Nostoc and bacteria 
seemed to have no appreciable effect on the quantity of nitrogen 
fixed. Bouilhae thus concluded that Schizothrix lardacea and 
Ulothrix Лассіда (either alone or in the presence of soil bacteria) 
and Nostoc punctiforme (in the pure state) are unable to fix free 
atmospherie nitrogen in the absence of combined nitrogen. 
The abundant fixation in the cultures containing а mixture of 
Nostoc and soil bacteria is not ascribed by the author to the 
activity of either organism alone. 
Richter (28) observed pots of soil with and without plants, 
some placed in the dark, others in the light. While a rich algal 
vegetation developed in the latter, none appeared in the former. 
Only in a few cases was the growth accompanied by a marked 
free-nitrogen fixation, but in these instances the author believes 
it due to the alge. Pure cultures were not employed. Benecke 
(1) contributed some observations made on cultures of Hormi- 
dium, Vaucheria, Cladophora, and members of the Conjugales,— 
all containing bacteria. In nitrogen-free cultures there appeared 
what Benecke termed “nitrogen-hunger,” a condition which is 
characterized in Hormidium by the production of very long, pale 
filaments, the cells of which become extremely long and in which 
the development of the chloroplast is so meager that the cells 
are almost colorless. Stocklasa (36) found that the “Alinit” 
bacteria fix free gaseous nitrogen in much larger quantities 
when grown in the presence of species of Stichococcus and Nostoc. 
This influence he considers to be due to the pentosans which, 
according to his belief, are present in large quantities in various 
alge, and which, because of their ready solubility in water, 
serve as a favorable energy-furnishing medium for free-nitrogen- 
fixing bacteria. 
A noteworthy contribution to the subject is that of Krüger 
and Schneidewind (19). These authors for the first time con- 
ducted extensive experiments with a variety of alge in pure 
culture, including Stichococcus chloranthus, S. major, S. bacil- 
