1914) 
SCHRAMM—GRASS-GREEN ALG AND ELEMENTARY NITROGEN 161 
is formed in the vaporization of water. Of interest are the 
observations by the same author on the unicellular grass-green 
alge, which he was unable to cultivate in solutions free from 
combined nitrogen. То these, therefore, he assigned the power 
of elementary-nitrogen fixation іп а much smaller degree than 
to Nostoc. 
Frank's conclusions were confirmed by the work of Schloes- 
ing and Laurent (31). These investigators supplemented the 
usual indirect method of analyzing the soil and harvest, with 
the direct method of determining at the beginning and at the 
end of the experiment the composition of the atmosphere in 
which the plants had been growing. To 2000 or 2500-gram 
quantities of a poor sandy soil 2.5 grams of limestone, 5 grams 
of a mixture of several rich soils, and a certain volume of a 
mineral nutrient solution containing, in some cases, a little 
potassium nitrate were added, and the whole placed in large 
flasks. In some, seeds of Jerusalem artichoke, oats, peas, and 
tobaeco were planted; others, to be used as checks, remained 
unplanted. То each flask were added 5 cc. of a liquid obtained 
by diluting 5 grams of rich soil with 20 cc. of water. After four- 
teen weeks, during which time the seeds germinated and pro- 
duced plants, the direct analytical method, confirmed by the 
results obtained by the indirect method, showed, except in two 
checks, an absorption of free atmospheric nitrogen. But the 
surfaces of the soils, during the progress of the experiments, be- 
came covered with green, cryptogamic plants, among which were 
mosses (Bryum, Leptobryum), and alge (Conferva, Oscillatoria, 
Nitzschia). This fact led the authors to repeat the first series 
of experiments, in every case suppressing the growth of chloro- 
phyllous cryptogams by covering the soils with a thin layer of 
dry, calcined, quartz sand. No trace of alge or mosses appeared, 
and, except in the case of the peas, no absorption of free atmos- 
pheric nitrogen was observed. This fact, together with the 
evident fixation of nitrogen in the checks of the first series (in 
which an abundant chlorophyllous cryptogamic vegetation but 
no phanerogamic vegetation developed), and the absence of 
fixation in those checks in which little or no algal growth devel- 
oped, led Schloesing and Laurent to conclude that there are 
some ‘‘inferior green plants” which are able to utilize free atmos- 
