24 R. A. EMErRSon 
gram KNOs, 0.25 gram K2:HPO,, 0.25 gram MgSOu,, and 0.25 gram NaCl. 
Other solutions of approximately equivalent molecular strength, but each 
lacking one of the nutrient elements of the complete solution, were used. 
In the nitrogen-free solution, 0.7 gram CaCl, and 0.22 gram K.SO, were 
substituted for Ca(NO3)2 and KNOs, respectively; in the phosphorus-free 
solution, 0.25 gram K»SO, for K:HPO,; in the potassium-free solution, 
0.2 gram NaNO; and 0.2 gram NaeHPO, for KNO; and KsHPO,, 
respectively; in the calcium-free solution, 1 gram NaNO; for Ca(NOs)s; 
in the magnesium-free solution, 0.3 gram NasSO. for MgSOu,; and in the 
sulfur-free solution, 0.2 gram MgCl: for MgSO,. A complete nutrient 
solution of four times the strength indicated above, 0.8 per cent, was 
also used, and one lot was given water without the addition of nutrients. 
After the first three weeks, the nutrient solutions were all used at double 
strength, 0.4 and 1.6 per cent, and clear water was occasionally given. 
This treatment, owing to considerable evaporation of water, doubtless 
resulted in a gradual increase in the strength of the solutions. The tests 
were carried on at the same time with one of the tests of rich and poor 
soil, so that the latter might serve as a check on the nutrient-solution tests. 
At first the seedlings given 0.2-per-cent complete nutrient solution 
reacted about as did those in poor soil, while those given 0.8-per-cent 
nutrient solution were no more highly colored than those in rich soil. 
At one month of age, the plants watered for three weeks with 0.2-per-cent 
and one week with 0.4-per-cent complete solution were growing rapidly 
and were no more highly colored than those in rich soil, while the plants 
in the very strong solutions (0.8 and 1.6 per cent) were beginning to 
wilt, perhaps from the toxic effect of the solutions. Thruout the remainder 
of the test, the plants given 0.4-per cent solution, alternated occasionally 
with clear water, were practically like those growing in rich soil both as 
respects vigor of growth and color development. 
In striking contrast to the plants given complete nutrient solution 
were the ones given clear water and those in nitrogen-free nutrient solution. 
Both these lots showed much color even at two weeks after germination, 
and soon thereafter the seedlings were red to the tips of their leaves. 
At the age of six weeks the plants of these two lots were much shorter 
and slenderer than those given complete nutrient solution. Their upper 
leaves were pale yellowish green, with much red, and the lower leaves 
were dead but still showing the red color that had developed earlier. 
