RESULTS OF EXPERIMENTS. 29 



criterion of toxic action, i. e., the death of the whole i)hint rather than 

 of the root tip alone, should not alfect the relative toxic influence of 

 the two salts. Coupin's results sho\ved that it required a 1.1 per cent 

 solution of sodium carbonate to kill wheat seedling-s, while only O.C) 

 per cent Avas necessary to produce the same effect when sodium bicar- 

 bonate Avas employed. 



As to the relative toxic order of the carbonate and bicarbonate, the 

 results recorded agree quite Avell with those of Sigmund," who found 

 that Avlieat development Avas retarded and germinating seeds of vetch 

 and rape Avere killed in a 0.5 per cent solution of sodium carbonate, 

 while the same concentration of sodium bicarbonate Avas quite harm- 

 less. 



Kearney and Cameron found sodium bicarbonate someAvhat less 

 toxic than sodium chlorid for the lupine, and, further, that a 0.02 

 normal solution of sodium bicarbonate permits plants to surviA^^ in 

 uuich better condition than in the corresponding concentration of the 

 chlorid. Kearney has also shoAvn by experiments that the bicar- 

 bonate is less toxic to maize than is sodium chlorid, the death point 

 for the bicarbonate being established at 0.05 and for the chlorid at 

 0.04 of a normal solution. 



In A^eAV of all these differences it Avill be no easy matter to decide 

 the relative harmfulness of these sodium salts. Experiments Avill 

 haA^e to be performed on a large number of plants of Avidely different 

 relationship before any definite conclusions can be reached. There is 

 great probability that the order of their toxicity is not the same for 

 all species of plants. This is A^ery Avell demonstrated by a compari- 

 son of the Avriter's results Avith those of Kearney and Cameron, Avho 

 found sodium sulphate more toxic to Lupinus (ilhus than sodium 

 bicarbonate, Avhile the Avriter found the rcA'erse to be true for Avheat. 

 There is a tendency among physiological experimenters to draAV gen- 

 eral conclusions for the Avhole plant kingdom from the results ob- 

 tained for a fcAv varieties, species, or genera, Avhich is absolutely 

 unjustifiable. Too much emphasis can not be used in condemning 

 such inferences. The results here obtained, it is thought, Avill hold 

 good for these particular varieties of Avheat, but they are not indica- 

 tiA^e except Avithin rather Avide limits of what others shoAV.'' They 



« Ueber die EiiiAvirkung Chemischer Agentien auf die Keimung, Laudw. A'ers. 

 Stat, 47: 2 (1896). 



6 This point is brought out in a most marked wAy by the work of Cameron 

 find Breazeale upon the effect of acids on wheat, maize, and clover, respectively. 

 (The Toxic Action of Acids and Salts on Seedlings, Journal Phys. Chem., vol. 

 S, No. 1, p. 1, Jan., 1904.) 



