1914] 
SCHRAMM—GRASS-GREEN ALG] AND ELEMENTARY NITROGEN 175 
30 grams) of sand was placed. For purposes of aération the 
separate series of flasks were joined together in groups of five, 
as shown in pl. 3 fig. 2, and the free end of the common 
connecting tube provided with three sets of triple wash-bulbs, 
--іһе two nearest the flasks containing nitrogen-free water, 
which served to moisten the air after passing through the third 
bulb containing 25 per cent sulphurie acid. In order to aérate 
any particular series of flasks it was only necessary to attach 
а filter pump to the rubber tube at the end of the series which 
it was desired to aérate and to open the pinchcock until the 
desired stream of air passed through the wash-bulbs. 
Chemicals.—The inorganic compounds used were all Baker and 
Adamson's analyzed chemicals; the organic compounds were 
Merck's highest purity chemicals. 
Cultural Solutions.—In the 1912 experiment, in which each 
series contained ten flasks, the following ten cultural solutions 
were used and in the following order, the flasks being numbered 
correspondingly: 
1. ХН,ХО; 0.5 grams, 
MgSO,7H;O 0.2 grams, 
K;HPO, 0.2 grams, 
CaClh.?H;O 0.1 grams, 
FeSO, trace, 
Nitrogen-free water 1000 grams. 
2. The same as No. 1, but containing 0.250 grams of NH,NO; in- 
stead of 0.5 grams. 
3. The same as No. 1, but containing 0.100 grams of NH,NO; in- 
stead of 0.5 grams. 
4. The same as No. 1, but containing 0.050 grams of NH4NO; in- 
stead of 0.5 grams. 
The same as No. 1, but free from combined nitrogen. 
The same as No. 5, but containing 2 per cent d-glucose. 
The same as No. 3, but containing 2 per cent d-glucose. 
The same as No. 5, but containing 2 per cent mannite. 
The same as No. 3, but containing 2 per cent mannite. 
The same as No. 3, but containing 2 per cent saccharose. 
ӘӘ o om 
1 
In the 1913 experiment, in which each series contained eight 
flasks, the following eight cultural solutions were used: 
