ACTION OF ALPHA-CROTONIC ACID ON PLANTS 
169 
and with crotonic acid. The famihar triangle system which has been used 
widely in a study of nutrient solutions and organic compounds was used in 
these experiments.'^ The essential constituents, P2O5, NH3, and K2O, of 
the three salts are present to the extent of 80 parts per million, but the 
composition varies. The details of the system, which are familiar to scien- 
tific investigators, are given in the publications cited, and only the general 
features of the triangle will be explained here. 
P2O5 
I 
;6 
K2O NH3 
Fig. 2. Triangular diagram, with the points representing the 66 culture solutions 
numbered. 
The triangular diagram shown in figure 2 is used as a guide. In this 
diagram the apices of the triangle, numbers i, 56, and 66, are the cultures 
which contain only the single salts, calcium acid phosphate, sodium nitrate, 
and potassium sulphate respectively, each containing 80 parts per million 
^ Schreiner, O., and Skinner, J, J. Some effects of a harmful organic soil constituent. 
U. S. Dept. Agr. Bur. Soils. Bull. 70, 1910. Ratio of phosphate, nitrate and potassium on 
absorption and growth. Bot. Gaz. 50: i. 1910. 
The triangle system for fertilizer experiments. Journ. Amer. Soc. Agron. 10: 225. 
1918. 
