124 M. M. McCooL 



In studying the toxicity of sodium and magnesium salts, Kearney and 

 Harter (1907) placed seedlings in salt solutions for twenty-four hours and 

 then transferred them to pure water. The inability of the roots to elongate 

 further was taken as an indication that the concentration used was fatal to 

 the root tips. Kearney and Harter made studies of the lethal concentra- 

 tions of pure solutions and of solutions with different amounts of calcium 

 sulfate added, employing as indicators a number of species of plants. 

 They found that the addition of calcium sulfate greatly diminishes the 

 toxicity of the sodium and magnesium salts to all the plants tested. 



Among the many experiments bearing on this problem reported by Loeb 

 (1905a) the following may be mentioned: The marine fish Fundulus soon 

 dies when placed in a pure solution of sodium chlorid. This is true even 

 though the solution may be no stronger than that which exists in sea 

 water. The toxicity of the sodium chlorid is counteracted by the addition 

 of chlorids of calcium or potassium. The calcium and potassium serve 

 primarily to counteract toxicity, and in this instance are unimportant as 

 nutrient elements; for when the fish is placed in distilled water it lives for 

 a considerable period of time. 



The brief indications given above may serve to show the direction and 

 importance of the work thus far undertaken. On the whole, many facts 

 have been presented concerning the antagonistic action of different bases 

 with respect to both animals and plants. Nevertheless, the data for the 

 seed plants are still insufficient, the evidences of slightly unbalanced con- 

 ditions on the development of the plants as a whole having received much 

 less attention. With respect to unbalanced conditions in the soil the 

 problems become most complex, and solution studies should make possible 

 a more nearly accurate approach to the agricultural application. 



The more recent work of Osterhout (1908, 1909) with wheat seed- 

 lings placed in pure and mixed salt solutions is important, but much 

 more data are required. His conclusions also are based on a comparison 

 of root gro^i:.h alone. Furthermore, it cannot be seen from his tables, in 

 many cases, to what extent one base antidotes another base. For example, 

 the root growth of wheat seedlings placed in solutions containing 100 

 cubic centimeters of .12 mol.* NaCl + 100 cubic centimeters of .12 mol. 

 NH4CI (the resulting concentrations of each salt being .06) is compared 



* As here employed, " mol. " denotes a gram-molecular solution, that is, one containing the number of 

 grams corresponding to the molecular weight of the substance dissolved to make 1 liter of solution. 



