True and Hunkel. The Poisonous Eflfect Exerted etc. 291 



Since the question of the life or death of the radicles after 

 an exposure to the various Solutions is a point important to 

 establish beyond doubt, great care was taken to in&ure certainly 

 here. By a System of measurements, it was possible to deter- 

 mine the growth of the radicle during and after an exposure to 

 the Solution. Experiments showed that Solutions of markedly 

 harmful action either bring about the death of the radicles com- 

 paratively promptly or the radicle fights a long-continued, losing 

 fight. Wishing to avoid decisions on the condition of radicles 

 known to be abnormal, it seemed best to accept the condition seen 

 after an arbitrary period had elapsed as the desired result. 

 Accordingly, radicles were exposed from twenty to twenty-four 

 hours to the action ot the Solutions and their condition after the 

 lapse of that time determined. 



In determining whether at this tinie the radicles were alive 

 or dead, several things were considered. The appearance of the 

 roots as regards, color, turgidity, etc., was carefuUy noted, The 

 growth made during the time spent in the Solution was ascer- 

 tained at the end ol the time of exposure by comparing the 

 distance from the India ink line to the tip with fifteen millimeters, 

 the invariable distance at the beginning of the experiment. 

 Usually some growth was found to have taken place, only the 

 stronger poisons causing death so soon as to show no elongation on the 

 second measurement. In order to ascertain if further growth was 

 possible, the radicles were returned to the Solutions and after 

 one or more days were again measured, If living at the end of 

 the arbitrary period of exposure, some undoubted growth would 

 appear. If none such was to be seen, and the superficial appear- 

 ance, the condition relativ^e to turgidity, etc., seemed to coufirm 

 the diagnosis, death was assumed. If the issue still remained 

 uncertain, another return to the Solution and another measurement 

 followed until some result could with a fair degree of certainty 

 be predicated. It was found to be useless to attempt to establish 

 with accurac}'^ the critical concentration, since variations due to 

 the biological factors involved were hardly calculable. 



Comparison experiments were also conducted in some cases 

 with Spirogyra. The methods used are described later under 

 the discussion of the action of phenol. 



The Solutions used were accurately prepared from trustworthy 

 chemicals. A stock Solution, made up on the basis of gj'aui-mole- 

 cules per liter, concentrated enough to cause prompt death to 

 the radicles, was used as a starting point. A number of dilutions 

 were then made, each of the series being half as concentrated 

 as that next stronger, and the radicles were immediately placed 

 in them. Tlius all the experiments of a series were made con- 

 temporaneously in fresh Solutions. Occasionally intermcdiate con- 

 centrations were interpolated when greater accuracy seemed likely 

 to be attained. By using stock Solutions made up at a strength 

 equal to some power of one-half a gram-molecule per liter of 

 Avater, we obtained chemical quantities standing in point of concen- 



19* 



