442 Dandeno— Relation of Mass Action to Toxicity. 



test here, as has already been stated, is the capability of mak- 

 ing further growth. In nice distinctions the mere appearance 

 is not a sufficient test; but strange as it may seem, this has 

 been the most general criterion. However, in the most critical 

 point this test fails. Jones (Theory of Elect. Chem., p. 269) 

 states : " It was a simple matter to determine when the root 

 was dead, since it lost its satiny lustre and acquired a dead 

 white color." This is just what it is almost impossible to do. 

 Cameron* gives it as a test of death that when the first 15 mm 

 became flaccid, death resulted. From this it may be inferred 

 that, if the radicle became flaccid the first 13 mm , or the first 

 10 mm , or even the first 5 mm , the seedling would be recorded as 

 living in that solution. Where the radicles did not become 

 flaccid at death he does not say how he decided the matter. 

 He contents himself with saying that it required muck experi- 

 ence and nice judgment. 



Vagueness is occasional even in measuring. Kearney and 

 Cameron (1. c.) state: "The radicle had somewhat elongated 

 from the plumule to the apex." They may mean from the 

 terminal bud to the apex of the root ; or, possibly from one 

 end of the radicle to the other, two very different things. 



The tables, contained in this paper (unless otherwise stated) 

 are records of average experiments of each type. It would 

 occupy far too much space to give all the records, because a 

 large number of experiments were made in each class, often as 

 many as twenty seedlings being submitted to the test. Experi- 

 ments were frequently repeated, sometimes out of mere curi- 

 osity, but all the evidence obtainable was used to strengthen 

 whatever results are here set forth. One or two seedlings, in 

 a test of this nature, is not enough. Occasionally a seedling 

 will die, even in water, and it is extremely difficult to tell why. 



To show an example of the comparisons of growth made in 

 regard to quantity of solution used, one experiment is here 

 below recorded. 



•uantity of 

 solution. 



I. 



Pea, HCln/2048. 



Growth in 24 hours 



in solution. 



In water, growth 

 in 24 hours. 



25 cc 





nmm 



nmm 



20 















12 















8 















5 





3 









9* 





12 





11 



1 





12 





16 



Such experiments as the one whose results are just given 

 form the basis for the figures in Tables II-IX. 



* Journal Phys. Chem. xiii, 3, 1904. 



