458 Dandeno — Relation of Mass Action to Toxicity. 



distributed on all sides, is not easy to say. Such a curling 

 is often seen in the radicles of corn seedlings grown in water 

 or in the ordinary water-culture media. Cameron (1. c.) gets 

 over the difficulty by saying: u They tended to curl up in an 

 apparent effort to leave the solution, seeking a more congenial 

 environment." This is assigning to plants a will-power we 

 were not aware they possessed. 



Summary. 



Quantity of solution has an important bearing upon its 

 power to affect the radicle; and rate of diffusion proves also to 

 be of some significance. 



Non-chemical* bodies retard very materially the activity of 

 the solute in bringing about death to the radicle. In some 

 instances the toxic effect was reduced 32 times by the mere 

 presence of pure sand. The mere presence of the walls of the 

 glass vessel has a perceptible effect in holding a substance 

 mechanically ; and the shape of the vessel is also not without 

 some effect. 



The action of the solute upon the radicle is very probably a 

 chemical one. 



There is no support to the theory of electrolytic dissociation 

 from the physiological side. In fact, certain substances pre- 

 sent phenomena which indicate opposition to it. 



Both the carbonate and the bicarbonate, if they dissociate 

 at all, do so in such a manner as to result in a chemical action 

 upon the water, forming a hydroxide as one of the products. 



Carbonic acid is of extremely low toxic power, killing the 

 radicle of the pea at w/342, but not the corn nor the lupine at 

 any concentration which it was possible to obtain (ti/171). 



Agricultural College, Michigan. 



* After this paper was written, an abstract of a paper by True and Oglevee 

 bearing, in part, on a similar line of investigation, appeared in Science 

 Mar. 11, 1904, p. 421. 



