﻿86 BOTANICAL GAZETTE [February 



which he found as much as three-fourths of the substance of 

 some spadices consumed within a few hours; yet respiration 

 need not use up the combustible material at any rate comparable 

 to this to make constructive growth impossible. 



Exactly the same phenomenon should be anticipated when 

 respiration is accelerated by a chemical stimulus as when heat is 

 the agent. The result of moderate stimulation will be a quick- 

 ening of the growth, but with a more violent stimulation of the 

 respiration, growth will be hindered and ultimately stopped. 

 Wherever my work has thrown any light on this question, it has 

 made this view seem more certainly the correct one. The more 

 concentrated the solutions used, the more is the respiration 

 accelerated, even when the concentration is fatal in twenty-four 

 hours or less. In the isolated case in my experiments, in which 

 with increasing concentration there was an initial decrease in the 

 respiration, the solution was so strong as to plasmolyse the cells 

 violently, and the result was without doubt due to the osmotic 

 (physical) action. In the relatively few instances in which it 

 has been sought, an optimum concentration for vegetative growth 

 has always been determined, and the known antagonistic effect 

 of considerably greater concentrations than those accelerating 

 growth shows that an optimum must exist for each stimulant 

 and plant. An optimum concentration of a chemical stimulant 

 for respiration is not known in a single instance; it does not 

 exist. 



The "biologische Grundgesetz" of Hueppe is not funda- 

 mental. It applies only to growth, or to growth and other 

 phenomena standing in the same relation with it to respiration. 

 It means merely that when respiration is not already too active, 

 accelerating it will result in a quicker growth. It is indifferent 

 whether the accelerating agent be chemical or thermal. The 

 explanation I have offered of the opposite effects on growth of 

 dilute and more concentrated solutions would do away entirely 

 with Richter's idea that the difference is because ions stimulate, 

 but molecules poison. As already stated, no difference exists 

 except in degree between solutions of different strength in their 

 action on respiration. Richter's explanation is difficult to 



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