﻿17S BOTAN'ICAL GAZETTE [march 



and nitrates of the same metals have the same toxicity, and the 

 relatively few contrary statements do not bear the stamp of 

 great probability. Coupin, for Instance, rates the relative effect- 

 iveness of LiCl and LiNOg as 12:5, and that of MnCU and 

 Mn(N03)2 as i : 13; Such a result is too surprising not to be 

 doubted until there is more evidence for it. That chlorids and 

 nitrates of the nutrient base often act differently in experi- 

 ments of long duration, when used as fertilizers, is partly due 

 to changes in the salts themselves. But working with salts 

 whose base acted mildly enough so that concentrations even 

 strong enough to cause plasmolysis could be used, it would 

 have been possible to detect differences in the toxic or stimu- 

 lating powder of CI or NO3 ions too insignificant to suggest 

 themselves at greater dilutions. Taken altogether, the NO3 

 ion has been a shade the more active in my experiments; but 

 there is no emphatic or constant difference in the stimulating 



action, in the effect on the turgor, or in the toxicity. 



jVI 



Up to — , the stronger the salt, the greater the stimulation, 



but the added stimulation by no means remains proportional to 

 the concentration; which is only another illustration of the gen- 

 eral rule that the less of any food Is present, the greater its 

 efificiency in proportion to the amount. 



I pass over any discussion of the probable mode of action of 

 K and Na, whether as food or stimulant, because in the present 

 state of our knowledge of the details of metabolism any such 

 distinction in the case of essential food elements Is difficult in 

 words, and imaginary in practice. 



The Elodea would always plasmolyze in 2 per cent. KNO 



when the experiments began. In all the experiments then in 



N 

 which a salt was applied in the concentration of — the cells 



must have been slightly plasmolyzed for a time. I was some- 

 what surprised that in such a case the extraction of water, as a 

 purely physical process, did not operate to depress the respira- 

 tion, but it seemed not to, as the acceleration was manifest from 

 the time the salt was applied. When still stronger solutions 

 are used, the physical action of extracting water and compres- 



