[Vor. 7 
14 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
mn green wt., “ngat 
y ^ /6Cor» ....- 
/ \ Ya 2 Pe as — A PA m ssi 
10 / \ — A^ EN / nct 
/ ^ 
AA / 7 
f N C e A CX P d A JAN B 6 
NA N 6 7 \ a 5 4 Ss m 
/ P d x p P d e 
av do a | Y eee 7) AL... 1%. LY 7 vete ue Gap 
Mu \ \ 9 pg 
3 \ Y 
7 \\ f 6 
IN Buse dine Wheat 
luo Ont Anko Orfo OTe lum MUY QV BuO Bul Ba Br BRO Bok o Bila BS Bao 
Py 34 $8 63 — 3% £4 335 35 66 64 56 $2 70 — 73 74 86 
I! 2 5 4 56 6 7 8 9 0 mm £ "5 Ww D 6 v 
Fig. 2. Total green weight of wheat, corn (3), and Canada field peas (3), in solu- 
tions A and B, with variations—chiefly in H-ion concentration. The base lines are 
drawn through cultures strongly acid, Py 3.4. 
A point of considerable interest, emphasized particularly by 
the results with peas, is that the range of most favorable growth 
with respect to hydrogen ion concentration differs materially 
with the constitution of the nutrient solution; thus the addition 
of acid to the B solution, although shifting the H-ion concen- 
tration towards that of the A solution, exhibits a corresponding 
rapid diminution of the growth quantities. From these data 
alone it is not possible to formulate an explanation of the fact 
last mentioned, but it is probably related in part to ionie condi- 
tions, in part to the composition and state of aggregation of the 
iron and calcium particles, or to other, indetermined factors. 
It should be pointed out, that in examining the curve, fig. 1, 
and all subsequent curves, a horizontal, or base line, is drawn 
through the growth quantity representing generally the unmod- 
ified solution A, so that all cultures may be compared with this, 
