1907] JENSEN—TOXIC LIMITS AND STIMULATION 23 
The experiment with soil was thrice repeated, and the results of 
each experiment are indicated in the curves, figs. 8, 9, 10. The 
separate tables are not given, but Table IV embodies the averages 
obtained from the three, as does also the curve, fig. 1z. The greatest 
stimulation, at 62/1000, falls off in concentrations both above and 
below this. If the control be considered “normal growth,” it will 
{ \ 
n/ 10000 - 5 
; H\ 
n/5000 : LU 
. oe "3 
N/ 1000 +. 7 — 
v a tet gee 
Oat Pin bens 
pect on tine 
an/ 1000 ne 
*, NX 
3n/ 1000 = ~— Nx 
52/1000 . en 
Pa 
gato ES om “ct 
dima Va 
/ Hee : 
it / 1000 7 7 
9 ae va of 
Be Joh ab gt 
n/100 = <r as ss 
BE et aa 
os ee 
an/r00} fat I 
I 3 a 
Itt : 
3n/t00 +o 
tery 
iff 
/ 100 
— 5 pi Be 105 
== 5 25 45 65 5 
ole eee 150 450 950 19050 1350 a 8 
ores 3s 65 95 125 155 = 
Fic. 8.—Lead nitrate series in soil. Nov. 19—-Dec. 20. 1905. 
be evident by reading jig. rz that all concentrations from n/too to 
”/10000 inclusive cause acceleration. Death occurs at 4m/100, a 
very slight elongation is shown at 371/100, and a little more at 21/100. 
Between 2n/too and n/1oo a rapid increase in growth rate occurs. 
In Comparison with CuSO,, therefore, acceleration may be caused 
by Concentrations very near the fatal concentration. 
In the solution series of lead nitrate, Table V and fig. 12, the 
death point lies at 4n/too to 2n/100, approximately at the same 
Concentration as in soil. Hence there is little if any indication of 
reduction of toxic effect, in so far as the death point is concerned. 
