1907] JENSEN—TOXIC LIMITS AND STIMULATION 21 
t 
elongation has taken place in concentrations above 3/1000; the 
curve of increase of growth rapidly rises as the concentration 
decreases, and much more rapidly than it does in soil. There is no 
indication of any acceleration in the photographed series, nor was 
H.O ' any acceleration found in 
F ; 
EP ieeis A. CuSO, solution culture, 
aes: although the experiment 
n/ 4000 4 ‘ . 
es es was twice repeated with di- 
m~ Sch. : 
n/2000 ~S$s5-| lutions as low as 11/100000. 
ee ad ye 
n/ 1000 Po i) ba i H.O 7 j 
ra yy / Li 
2n/ 1000 ; icf n/ TOQO000O E oy 
- 
4n/ tooo Cid oe 7 n/'75000 
6n/t000 / "3 rf n/ 50000 I 
5 ; 
Fa we / WH 
8n/1000 +— f é CF n/ 25000 i/ 
! i) 
n/ too tot 7 : i n/ 10009 7 
nya ; Pe 
2n/t0oo}—__| / eae al n/ 5000 7 
4 | Z 
j i 
3n/ x00 ag n/ 1000 = 
ca SA 5 10 15 ee ia renee 500 1300 
Se 20 30 4° 50 Sig eee 120 160 
Io0o 
sear 10 “ne “ oa c. 5.—Copper _ sulfate 
Fic. 4.—Copper sulfate series in soil. Feb.17- series in solution. Feb. 
Mar. 3. 1906. Mar. 3. 1906. 
As has already been stated, the fatal concentration of CuSO, in 
solution cultures is approximately one tenth that of the fatal concen- 
tration in soil; or, the quartz has reduced the toxic effect about 
nine teaths. 
Tables I, II, III follow and curves (figs. 4, 5) precede. From 
these it will be seen that the traaspiration, the length of sprout, and 
the green and dry weights vary quite uniformly. 
TABLE I 
CuSO, sERIEs IN SOIL; 12.5% MOISTURE. FEBRUARY 17-MarcH 3. 1906 
an_| 60 | 80 | _m | 2m | 30 
n n n 2n 
1000 | 1000 | 000} Too | Too | 100 
10000! 4000 | 2000 | To00 | 1000 
HO 
Av, length of s 6| 8.02| 7-26) 4.10) 3.42 
- jprout, cm 18.06/17. 76117. 70|20.68| 18. 44/16.96)11.98/ 11-5 ‘ 
Eh transpiration, gm....| 41.6137.9 |30.4 |52-0 |35-4 |30-2 \24.8 (23.8 — pet ae 13-9 
green weight, mg... . 6 8 7 | 530 | 450 | 400 
aa ey sce | 5 | 9 | 88 | 22 | 98 8 | “| S| “S| “| 
dry weight, mg 
