﻿176 BOTANICAL GAZETTE [march 



The work on chemical stimulants was concluded with tests of 

 some of the common mineral foods. Of these, calcium nitrate 

 caused a more active evolution of CO^ from Elodea, but as it was 

 found to have the same effect on tap water, its action on the plant 

 was of questionable nature, and the table showing its effect is 

 omitted. Sodium chlorid and nitrate, and potassium chlorid, 

 nitrate, sulfate, and iodid were all tested as to their action on 

 tap water, from which none of them caused any escape of CO^. 

 To report the individual experiments showing this would be 

 superfluous. Excepting a number of them which illustrate an 

 altogether novel point in connection with the death of the 

 plants, the individual tables of the results of the application of 

 these salts can also be dispensed with, and their places will be 

 taken by a single table showing the per cent, of acceleration of 

 respiration. This per cent, is computed from what seems to me 

 to be so much of the results of the experiments as represent the 

 action of the salts on sound, unacclimated plants. 



When any of these salts were applied to the plants in con- 



centrations of — to — there was a prompt increase in the rate 01 



respiration. This quickened rate remained constant in most 01 

 the experiments for a period of from twelve hours to more than a 

 day; then it fell steadily or rose rather abruptly. The per cent, 

 of acceleration is figured from the steady rate following the 

 application of the salt, as compared with the preceding hours. 

 The length of this period of uniformly accelerated respiration 

 depended on the condition of the Elodea, on the nature of the 

 salt and its concentration, and on the temperature, being shorter 

 at higher temperatures. 



The desired concentration of these salts was near enough to 

 their limit of solubility so that applying them like the strong 

 poisons would have introduced a possible source of large error 

 in the CO^ dissolved or soluble in the solution applied. This 

 was avoided by the method employed with iodin (table XXX), 

 letting the COg-laden air from each Elodea culture pass 

 through another bottle containing the salt to be applied. Thus, 



if I had 2N KCl, and wished to test — , the Elodea was placed 



10 



