go BOTANICAL GAZETTE [ AUGUST 
to have taken place before death, sometimes nearly equal- 
ing the normal under the prevailing conditions of temperature, 
etc. It was thus possible from the ante mortem growth in a 
series of solutions to locate roughly the concentration limit 
sought. 
When neither aspect nor growth rate gave plain evidence, the 
radicles were measured and returned to the solutions to be again 
observed. If between the last observation and the first, no elon- 
gation had occurred, it was inferred that the roots were dead at 
the time of the former inspection. 
Since, as the concentration decreases, an increasingly long 
exposure is necessary to work fatally, it was decided to choose a 
period of exposure to the solutions within which the action of the 
same should be judged. This period was from fifteen to twenty- 
four hours following the introduction of the roots into the solution. 
Although the time limit may seem rather broad, it must be borne 
in mind that solutions were always diluted by one-half, and there- 
fore witha Strong time limit, we should still be far from any 
absolute concentration limit.% Individual differences in the 
seedlings frequently show themselves, one radicle at times being 
killed, another beside it surviving. In such cases, the first suf 
viving individual indicated the concentration sought. 
Usually two seedlings were placed in each concentration 
tested, but Sometimes only one was used, When grounds for 
doubting the accuracy of results were present, experiments in 
question were repeated. 
It is not to be inferred that the limits here obtained represent 
the greatest strength of the given substances that these radicles 
can endure, since a gradual increase of concentration allows 4 
very considerable accommodation on the part of the plant to be 
made, and the consequent toleration of solutions that would 
upon immediate use have proved fatal. This was shown in sev 
eral experiments in which dead roots were left for a time in the 
solutions. Laterals pushed out above the dead region and grew 
in the solutions without serious harm, ~ 
‘SP. Klemm, zd¢d., 33 (for acids), 
