1912] SCHREINER &• SKINNER— FERTILIZER SALTS 37 



again showed strikingly the influence of phosphate in overcoming 

 this effect, the general appearance of the entire triangle of cultures 

 being similar to that already described. The effect of the cumarin 

 was to depress the green weight from 100 to 75 in this second 

 experiment, this being the average depression for all the cultures 

 in the set. Here, as in the first experiment, the toxicity of the 

 cumarin was lessened most in the solutions high in phosphate, 

 being 85 per cent of the normal as compared with 74 and 70 per 

 cent in the cultures high in nitrate and potash, respectively. 



The line of cultures containing no phosphate whatsoever again 

 showed the greatest effect of the cumarin; this harmful influence 

 becoming less and less until complete recovery of the plants is 

 noticed in the cultures containing higher amounts of phosphate. 

 The total absence of phosphate showed a depressed growth equal 

 to 62 per cent of the normal; this rises to 70 per cent on the addi- 

 tion of 8 ppm., and to 76 per cent on the addition of 16 ppm., and 

 so on upward, somewhat irregularly but definitely, until in the higher 

 concentration of phosphate the effect of the cumarin is lost entirely. 



The foregoing experiments show clearly the influence of cumarin 

 on growth and the effect of phosphate in counteracting the harmful 

 influence of the cumarin. There remains to be considered the in- 

 fluence of the cumarin on the concentration of the solution during 

 the growth of the plant. 



Mention has already been made of the fact that the concen- 

 tration differences produced by the growth of the plants in the 

 various cultures was determined by making an analysis for nitrate 

 at the termination of every three-day change, and of the phosphate 

 and potassium on a composite of the solutions from the four 

 changes. It is thus possible to compare the results obtained under 

 the so-called normal conditions without the cumarin and under the 

 conditions where 10 ppm. of cumarin were present in the solution. 

 The 36 cultures comprising the fertilizer combinations in which 

 all three fertilizer elements are present were consistently analyzed 

 and these only are here considered. 



The amount of total P 2 O s +NH 3 +K 2 removed from solution 

 by the growing plants in the total number of 36 cultures was 1379 

 milligrams under the normal conditions and 1272 milligrams in 



