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J. J. SKINNER AND F. R. REID 
in others. The growth is more nearly normal in the solutions high in 
phosphate, but is much depressed in the solutions in the lower part of the 
triangle, that is, in those low in phosphate. 
In table 2 are given the green weights of the various series of cultures 
containing the same amount of phosphate, that is, the series along any one 
of the horizontal lines in figure 2. 
The last column of the table gives the percentage decrease caused by 
the crotonic acid. In those cultures which contained 80 parts per million 
P2O5, growth was reduced 30 percent, and in the cultures containing 72 
parts per million P2O5, 42 percent, while in the cultures containing 32 parts 
per million of P2O5 and less, growth was reduced as much as 55 percent. 
Fig. 4. Green weight in grams of wheat plants in nutrient solutions containing varying 
ratios of phosphate, nitrate, and potash, the source of P2O5 being calcium acid phosphate, 
(i) Without crotonic acid, and (2) with 25 p.p.m. crotonic acid. 
In another experiment similar to the one just described, the crotonic 
acid was used in amounts of 25 parts per million. In all other details the 
two experiments were similar. This was conducted February 14-26, 191 7. 
The green weights of the two sets of plants are given in the charts in figure 4. 
There is a difference in growth of 35 percent. The crotonic acid was mark- 
edly harmful in the nutrient solutions even with this concentration. 
By an examination of table 3, where the cultures are arranged according 
to their P2O5 content, it is again seen that calcium acid phosphate was very 
effective in overcoming the crotonic acid. 
The lessened toxicity of crotonic acid in solutions high in phosphate is 
also shown when the results of the experiment are grouped in such a way as 
to obtain all cultures containing 50 percent and over of any one of the three 
constituents P2O5, NH3, and K2O. This is accomplished by taking the 
cultures contained in the smaller triangle formed at each angle of the larger 
one shown in figure 2, that is, the cultures contained within the triangles: 
1-16-21; 21-61-66; and 16-56-61 respectively. 
