406 BOTANICAL GAZETTE [JUNE 
TABLE I—Continued 
RADICLES IN COPPER SULFATE SOLUTIONS = CONTROLS IN DISTILLED WATER 
* | Average growth Growth of » | Average growth 
Concentration | Time in solu- | Total growth per hour correspondi per hour 
tions in 1 hours ee ees in mm contrer ¢ in mm in mm 
n/275,000.... 19.0 11.8 0.61 14.2 0.74 
19.0 I1.0 0.57 10.3 0.54 
18.0 7:8 0.42 15.0 0.83 
n/300,000.... 19.0 II.2 0.58 14.2 0.74 
oe 10.3 0.54 11.5 0.60 
19.0 I4.0 0.71 10.3 0.54 
18.0 6.0 0.33 15.0 0.83 
n/ 400,000... . 19.0 10.0 O.52 41:58 0.60 
18.0 12.7 0.70 15.0 0.83 
24.0 14.8 61 15.8 0.65 
n/500,000.... 18.0 16.0 0.88 15.0 0.83 
24.0 3°97 0.57 15.8 0.65 
ee 
Observations were next made on the growth rate to ascertain 
whether the retardation occasioned a gradually increasing lag in rate 
of elongation, or an abrupt termination of growth due perhaps to 
the sudden failure of vitality in the cell. Table II shows the average 
growth of several groups of four radicles, each selected from the various 
concentrations, and of the corresponding controls in distilled water. 
The several growth periods recorded for each concentration were 
consecutive. 
With one exception, growth was in every case less in the coppeT 
sulfate solution than that made by the control in distilled water. In 
the higher concentrations growth was practically inhibited at the 
end of a twenty-four hour period. Passing down the series the growth 
is seen to be gradually diminished after the first twenty-four hours. 
A similar reduction in growth rate is apparent in the controls, though 
in a degree much less marked. 
The observations summarized in tables I and II indicated that 
the series of concentrations selected would afford material showing 
strong toxic action resulting ultimately in death (x/20,000 to m/ 50,000); 
as well as the more prolonged and gradual though no less fatal effect 
of higher dilutions. 
