i9i 2] SKINNER— CREATININE AND CREATINE 157 



composed of fertilizer mixtures having more than 24ppm. of 

 nitrate was uncertain; in 



some 



growth and in others there was a slight decrease, that is, the growth 



amounts 



same 



Before discussing further the effect of creatinine, it will be 

 necessary to recall the effect which nitrates have on the growth of 

 plants in mixtures of the other two fertilizer ingredients potash and 

 phosphate. In work previously published, 5 it was shown that the 

 better growth occurred in the normal cultures when the three fer- 

 tilizer elements P 2 s , NH 3 , and K 2 were present. It was best in 

 mixtures which contained approximately equal amounts of NH 3 

 and K 2 and a small amount of P 2 5 (about i6ppm.). The 

 growth in the cultures containing the three constituents was much 

 greater than in the cultures containing only two constituents. 

 This was especially marked when nitrogen was not in the compo- 

 sition. In illustration of this, the average growth of a number of 

 cultures, composed of mixtures of phosphate and potash in amounts 

 of 8oppm. of P 2 5 +K 2 0, was 1.000 gram against 3.155 grams as 

 the average growth of cultures composed of mixtures of these two 

 ingredients, with an addition of only 8 ppm. of NH 3 as nitrate, the 

 total concentration of nutrients being the same. In a second 

 experiment conducted in a similar manner, but at a later date, the 

 average growth of the cultures, composed of mixtures of phosphate 

 and potash, was 0.878 gram, and the average growth of cultures, 

 in mixtures of the three ingredients, containing 8 ppm. of NH 3 as 

 nitrate, was 2 . 107 grams. 



In the present experiment the growth in the normal cultures 

 composed of varying proportions of phosphate and potash, com- 

 pared with the growth in mixtures of these two ingredients, with 

 8 ppm. of NH 3 as nitrate added, is given in table IV. By a close 

 examination of the figures in this table, it is seen that the growth 

 in the mixtures of phosphate and potash is smaller than in cultures 

 composed of mixtures of the three ingredients, though containing 



5 Schreiner, O., and Skinxer, J. J., Ratio of phosphate, nitrate, and potassium 

 on absorption and growth. Bot. Gaz. 50: 1. 1910. Some effects of a 1 

 soil constituent. Bull. 70, Bureau of Soils, U.S. Dept. Agric. 1910. 



irm 



