58 LON A. HAWKINS 



allow germination, this being abnormal, however, with the production of 

 unusual and characteristic structures. (3) Germination may be inhibited 

 for eighteen hours, the spores germinating when subsequently transferred 

 from the toxic solution to distilled water. (4) The spores may be killed 

 in eighteen hours and thus be incapable of renewed activity even when 

 transferred to water. It was usually possible to bring about these four 

 types of response by means of any one of the compounds used in this study 

 by a proper choice of concentration. An arrangement of these substances 

 in the order of their toxicity, as evidenced by the inhibition of spore 

 germination, is found to hold also for their effectiveness in bringing about 

 the other and less final changes which lead to abnormal growth. A list 

 of the substances employed, arranged in the order of their toxicity follows : 

 Cu(N0 3 ) 2 , CuS0 4 , Pb(N0 3 ) 2 , A1(N0 3 ) 3 , HNO 3 , Zn(NO 3 ) 2 , Ni(NO 3 ) 2 , 

 Mg(NO 3 ) 2 , Ca(NO 3 ) 2 , KNO 3 , sucrose. 



It is shown that no one of the several hypotheses heretofore proposed to 

 account for the dynamics of the antagonistic salt action is adequate to 

 explain all the facts brought out in this study. 



INTRODUCTION. 



Numerous instances have been recorded of the influence of salts on the 

 toxicity exerted by various substances upon organisms. This antagonistic 

 action, as it is frequently called, of a salt upon a toxic substance, is of 

 considerable importance in influencing the behavior of organisms in a 

 given environment, or indeed in determining whether or not they may 

 exist at all in certain environments. For example, Loew 3 has shown that 

 the toxic effect on Spirogyra of a one per cent, solution of magnesium 

 nitrate is inhibited by the presence in the medium of a 0.3 per cent, solu- 

 tion of calcium nitrate, while Loeb 4 has demonstrated that the addition of 

 a small quantity of a calcium salt to a 0.625111 solution of NaCl inhibits 

 the toxic effect of the NaCl on the development of Fundulus eggs. Oster- 

 hout 5 has shown that a physiologically balanced solution, containing sodium 

 chloride, magnesium chloride, magnesium sulphate, potassium chloride and 

 calcium chloride, is necessary for the best growth of certain marine algae. 

 True and Bartlett 6 have brought out the fact that a ratio of one molecule 

 of calcium to nine molecules of magnesium inhibits the toxic effect of 

 rather high concentrations of magnesium upon roots of Canada field 



3 Loew, O., Ueber die physiologischen Functionen der Calcium- und Magnesium-salze im Pflanzen- 

 organismus. Flora 75: 368-394. 1892. 



4 Loeb, J., Ueber den Einflus der Werthigkeit, und moglicherweise der elektrischen Ladung von 

 lonen auf ihre antitoxische Wirkung. Archiv ges. Physiol. 88: 68-78. 1902. 



5 Osterhout, W. J. V., On the importance of physiologically balanced solutions for plants. I. Marine 

 plants. Bot. Gaz. 42: 127-134. 1906. 



'True, R. H., and Bartlett, H.H., Absorption and excretion of salts as influenced by concentration 

 and composition of culture solutions. U.S. Dept. Agric. Bur. Plant. Ind. Bulletin 231. 1912. 



