428 AMERICAN JOURNAL OF BOTANY [Vol. 9, 
Experiment II 
Behavior of Nitrates when Total Concentrations are Reversed 
In the foregoing experiment the three solutions differed in total con- 
centration as well as in the concentration of nitrates. It happened that 
the solution with the highest nitrate content had also the highest total 
concentration. The question is naturally raised, then, as to whether or 
not the increased concentration of the solution rather than the increased 
nitrate content is responsible for the increased ratio of tops to roots. This 
question has led to the arranging of a second experiment in order to throw 
light on this phase of the problem. It is recalled here that Stiles and Miss 
Brenchley found that the top-root ratios decreased as the concentration 
was decreased. 
For this experiment. Solution II (medium nitrate) remained as in 
Experiment I. The low-nitrate solution is modified and designated Solu- 
tion la. In this, the nitrate content is kept the same, but the other salt 
components are increased to .5 gram per liter, which makes the modified 
solution about 5 times the original, Solution I. The high-nitrate solution is 
designated Solution Ilia; it likewise retains the same amount of nitrate 
as before, but the remaining six salts are reduced to .06 gram each, thereby 
reducing the total concentration of the solution about one seventh. The 
composition of the solutions used in Experiment II was as follows: 
Sol. la 
Sol. II 
Sol. Ilia 
(Low Nitrate) 
(Medium Nitrate) 
(High Nitrate) 
KN03 
.025 
•25 
•5 
KH2P04 
•5 
.1 
.06 
K2S04 
•5 
.1 
.06 
Ca(N03)2 
.025 
•25 
•5 
Ca(H2P04)2 
•5 
.1 
.06 
CaS04 
•5 
.1 
.06 
Mg(N03)2 
.025 
•25 
•5 
Mg(P04)2 
•5 
.1 
.06 
MgS04 
•5 
.1 
.06 
Total 
3.075 
1-35 
1.86 
The highest concentration here is somewhat above that of Sachs' 
solution mentioned above. The newly made solutions had the following 
pH values: Sol. la, 5.59; Sol. II, 6.24; Sol. Ilia, 6.24. Iron was supplied as 
in Experiment I. 
Twenty cultures were set up for each solution in the same manner as 
previously described. Four of these, constituting a series, were harvested 
every two weeks. The solutions were changed weekly, but were filled up 
every day to make up for water lost. The experiment began October 28, 
1920, and ran for 56 days. Dry weights only are recorded. 
Weather conditions throughout the duration of this experiment were 
not favorable for plant growth ; the continual cloudiness together with the 
late autumn season made for much less growth in this set of experiments 
