[Vol. 2 



542 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



T 



at first but became 



31, where the tips were slightl 



almost normal in the water after 7 days. 



In the temperature experiments we have thus used the ex- 

 tremes of temperature and have reduced the interval of expo- 

 sure in order to approach the point at which the effect is just 



evident. 



VII. Effects of Anesthetics in Solution 



Having seen some of the effects of anesthetic vapors, we 

 may turn our attention next to the results obtained with anes- 

 thetics in solution. In the investigations of others pertaining 

 to the effect of anesthetics, already cited, the result has been 

 almost universally noted that small amounts of anesthetics 

 decrease the exosmosis of coloring matters, etc., while toxic 

 amounts increase it. In most cases this exosmosis was ex- 

 plained on the basis of an alteration in the plasma membrane, 

 small amounts of the anesthetics presumably reducing the 

 permeability and large amounts increasing it. But a point 

 worthy of note is that wherever such effects have been deter- 

 mined the substance under observation was either a colored 

 compound or one of complex organic nature. 



Thus Czapek ('11) used the myelin-formation of a tannoid 

 substance, anthocyan, as a basis of observation. From the 

 standpoint of a physical phenomenon, i. e., the lowering of 

 surface tension, his experiments beautifully illustrated the 

 principle under consideration. But from the standpoint of 

 exosmosis in the broader sense we must include electrolytes 

 (salts, bases, and acids) as well as tannin compounds in any 

 discussion dealing with agents affecting exosmosis, and while 

 the critical concentrations which he determined are undoubt- 

 edly characteristic of the plants and the compounds studied, 

 the results given herewith show that they are not the limit- 

 ing concentrations which effect the exosmosis of electrolytes 

 from the roots of certain plants. The limiting concentrations 

 which he found are given in table iv. 



Czapek believed the permeability of the plasma membrane 

 was altered under the influence of alcohols, ethers, etc., so that 

 abnormal exosmosis occurred. Whatever may be the expla- 



