﻿1903] 



CHEMICAL STIMULATION 



181 



\ 



This excessive evolution of CO^ is undoubtedly a feature of 

 the death of the plant. It is not easy to fix a time at which it 

 begins, because the cells in a single leaf do not all die together ; 

 but it is conspicuous while a very large part of the material 

 IS still evidently alive. It continues after the entire material, 

 judged b}' its appearance under the microscope or by the test of 

 plasmolysis, would be called dead. Two conceivable sources of 

 this COo suggest themselves; it might be allowed to escape by 

 the removal of an obstruction when the protoplasm dies, as the 

 acid in sour leaves 



rophyll ; or else its origin is in the protoplasm itself. As we 

 have every reason to suppose, and none to doubt, that CO 



gets an opportunity to destroy the chlo- 



diff 



2 



uses readily through the living protoplasm, the first of 



these suggestions may be dismissed, and we may accept it 

 as a fact that the escape of a large amount of CO3 is not merely 

 an accompaniment of death, but is a part of death. 



If the phenomenon is thus fundamental in the demise of the 

 plant, it must occur under other fatal conditions beside poison- 



TABLE XXXIX. 

 December 10. Elodea at 39-41° C 



mg. 



Time 



6:30- 8 :05 



8:05- 9:05 



9 -'05-10: 05 

 IO:oS-ir :05 

 II ■•05^12: 05 



12:05-11:05 (II hrs.) 

 11:05- I : 05 



Control 



In the experiments m 

 which plants were boiled there 

 was an amount of CO^ evolved 

 for which I was at the time 

 quite unable to account. And 

 I have had several opportuni- 

 ties to observe an increase of 

 apparent respiration as Elodea 

 succumbed to prolonged expos- 



ure to too high a temperature. 



Two of these follow ; the first is an extract from the same experi- 

 ment as table XI, showing the behavior of the control later in 

 the day; during the hours included in table XI the control had 

 been reasonably steady. 



In the experiment recorded in table XL the rise in the con- 

 trol occurred in time to invalidate the results of the experiment 

 cuitu 



0.087" N. per hr 



0.105 



O.IOO 



0.150 



0.135 

 0.143 



0.II7 



re. 



While I have observed this feature of death only as a result 

 of poisoning and of heat, it appears to me very possible that the 



