* 
IN Mixep Solutions 391 
and determined the strongest concentration in which the plants 
were able to make appreciable growth. This point of undoubted 
growth furnished a point of departure in making comparisons. The 
TaBLe | 
SIMPLE SoLuTions.* HEAvy METALS. AVERAGE GROWTH-RATES IN MILLIMETERS tT 
Conc. Gm. Mol. | Cuso, | uci, | Cu(CH,CO.), | AgNO, | HgCl, | ZnSO, 
a8 an | piece ao eet httad 
m/8192 | | 2.0 6.0 
m/16384 | a aad eee 1.0 9.0 9.0 
m|32768 TO Bees ee 2.0 13.0 18.0 
ml65536 | : ie) 0 2.0 16.0 18.0 
(9553 K ieee pa 3 | ie 
m/131072 | 11.0 10.5 If.0 6.0 16.0 
m/262144 | | 16.0 | 15.0 | 13.5 
m|/524288 | | | 22.0 REE E 
Check. | EC ho Semeues pee 9s a | 120 12.5 15.0 15.5 
* All control experiments in this and subsequent series were made in water which 
had been very carefully distilled several times. All of the solutions were prepared from 
distilled water obtained under constant conditions. 
+ The growth-rates recorded in these tables are those for the first 24 hours. 
accompanying tables give the average growth-rates at the end of 
twenty-four hours. 
Table I summarizes the growth-rates obtained in a series of 
solutions of salts of copper, silver, mercury and zinc. In order 
Tasce II 
Smmp_Le SoLuTions. LIGHT METALS AND UREA, AVERAGE GROWTH-RATES 
IN MILLIMETERS 
ota, | NaCl | Na,SO,} KCI | KNO,| Ca(NO,), | CaCl, | CaSO," MgCl, | Urea 
| 
m3 | ae 0.5 
m/16 2.5 9.6 1.0 
| 32 25 1.3 | 07 3.4 20.0 16.0 35 
m|64 7.5 1.0 | 20] 4.0 20.5 35-0 .O 
m/1t28 ro5 2:85 1 © 6.654 8.0 21.0 
m/256 5.8 | 701 4,0 21.0 
m/512 35 
m|1O24 | 2 
m|2048 | | 9-4 
m|4096 i 4 | | 12.5 
Check. | 15.5 | t00 | 10.0 | 14.0| 100 | 12.5 | 13.0 | 10.0 | 15.2 
to test the possible antagonizing influence of compounds with 
other bases, a number of salts of sodium, potassium, calcium and 
magnesium were used. 
-A similar point’ indicating the maximum concentration per- 
