﻿1903] CHEMICAL STIMULATION 1 83 



the subject. The evolution from plants killed by K and Na 

 decreased after they had been dead a few hours. The solubih'ty 

 of COg in water makes my usual method of experimenting inap- 

 propriate to the determination of a time when CO3 may cease to 

 be evolved. I have tried one experiment which proved that if 

 Elodea is left in water and kept at about 90*" C. the evolution 

 of COg gradually diminishes, but at the end of four days is still 

 as rapid as in the ordinary respiration of the same plants. As a 

 control the same amount of material was placed in so little water 

 • that it became dry within twenty-four hours, and the evolution 

 I of COg fell to a trace, without, however, quite ceasing. The 



material'was again wetted and considerable CO3 was evolved, 

 though less than from the material which had been kept in water. 

 It would appear from this that the usual dry-weight determina- 

 tions are practically valid, and a number of tests which I have 

 made with seeds show that at most a trace of CO^ escapes as 

 they dry at 100^ C, or even a few degrees higher. 



I 



SUMMARY. 



The method has been perfected until the results are reliable 

 to one-fiftieth of a milligram. 



No poison has been found not to act as a stimulant. 



Metallic salts drive CO^ from carbonates in the cell sap. 

 This pseudo-respiration, under the action of strong poisons, is 

 many times as active as the real respiration, and makes the study 

 of the latter impossible. 



COg is given off from filtered sap squeezed from Elodea much 

 more rapidly than from the Elodea before injury. 



The stimulation by K salts is greater than that by Na salts, in 

 about the proportion of their relative toxicity. No constant 

 difference was found between chlorids and nitrates. 



A considerable evolution of CO^ is a feature of the breaking 

 down of '' protoplasm" into mere **proteid," in death. 



Leland Stanford Junior University, 



California. 



