1910] SCHREINER & SKINNER—ABSORPTION AND GROWTH 25 
The first column gives the percentage composition of the fertilizer 
mixture so far as the P,O, content was concerned. In the third 
column is given the average concentration for the eight three-day 
periods in the experiment, and in the fourth column, the difference 
between this and the original concentration, thus giving the average 
decrease, which is expressed as a percentage in the fifth column on 
the basis of the original concentration. The sixth column gives the 
average green weight obtained along any of these concentration lines, 
and the next column gives the decrease in P,O, calculated to the unit 
basis of one gram production of green plant. In other words, the 
decrease recorded in the fourth column has been divided by the 
green weight corresponding thereto in the sixth column. This gives, 
as it were, the rate of decrease in parts per million of the solution for 
each gram of green weight produced; but if it is desired to have the 
result expressed in terms of milligrams of P,O, removed by each 
gram of green weight produced, the figures in the column must be 
multiplied by 2, since 250 cc. of solution were presented to the plants 
eight times; i.e., a total of 2000 cc. It will be noticed that the green 
weight steadily increased as the phosphate content decreased. It 
must be borne in mind, of course, that when the phosphate content 
decreases, there is a corresponding increase in the average content 
of both potash and nitrogen. In the last-figure for the green weight, 
however, namely that in which the phosphate content became zero 
in the culture solutions, there is again a marked drop, although the 
potash and nitrogen content in these was higher than in any of the 
solutions above this in the table. It follows accordingly that a very 
distinct part was played by the phosphate in producing growth, 
although its maximum efficiency seems to be reached in these experi- 
ments in rather low concentration. Attention might also be called 
here to the fact that the concentrations of phosphate in soil solutions 
are always low, and relatively much lower than any of the other 
constituents here considered. The plant in its natural environment, 
therefore, has adapted itself to the occurrence of this constituent in 
weak solutions. 
The increase in green weight shown by the table to be from 3.1 
to 3.6 grams corresponded to an increase from o to 8 ppm. in the 
original P,O, content. The further increase to 16 ppm. P,O, has 
