26 BOTANICAL GAZETTE [JULY © 
produced no further increase in plant growth, and above this a decrease _ 
has even followed, which may be in part due to some direct influence — 
of the phosphate solution, the carrier here used being calcium acid — 
phosphate, and may also be due in part to the fact that the quan- 4 
tities of potash and nitrate are being decreased as the phosphate — 
increases. This relation, however, has been discussed in a much 4 
of most absorption and least change in the ratio. All these regions 
it will be noticed comprise solutions which contain low amounts 
Om PO,. 
The average concentration of phosphate in the culture solution 
after growth, as shown in the third column, continually decreases 
The actual decrease in the next column, however, shows that the 
greatest decrease in concentration of this element does not go wi 
the greatest growth, but is found in the 40 ppm. phosphate solu 
tions, increasing steadily from the 8 ppm. solution to this point 
other fertilizer elements entirely disappear and only phospha 
remains, when it again drops slightly, the conditions for growth a 
being much poorer through this total absence of potash and nitrogen 
The decrease when expressed as a percentage of the amount of mate 
rial originally present shows that the removal is the more complete 
as the original concentration is lower. The last column in this section 
of the table, giving the decrease per unit of green weight, shows that 
equal weights of green plants cause quite unequal decreases in con- 
centration, this change being least in the weaker solutions and greates' 
in the higher, thus indicating that more was removed by the plant 
in the higher concentrations than it could economically utilize : 
the conditions; i.e., the plant absorbed the material because it 1 
there, although it apparently had already all that it could utilize 
economically. This is a fact consistent with field observations 4 
ash analysis, where it is frequently noticed that the actual am 
of mineral constituents is larger in the poorer plants. 
