13S University of California Publications in Agricultural Sciences [Vol.3 



present problem or work so recent as not to be included in the papers 

 cited above. 



A large share of the contribution to the experimental evidence in 

 regard to antagonism between salts as regards plants we owe to Oster- 

 hout. In a series of papers he has shown that any salt may be toxic 

 to plants when used alone in solution at certain concentrations and 

 further that the addition of a second salt may, in proper concentra- 

 tion, modify or eliminate entirely the toxic effect of the first salt. He 

 has shown further that acids, alkalies, and various organic compounds 

 may likewise be toxic to plants and that their toxic effects may be 

 modified by the presence of a variety of compounds, depending upon 

 the toxic substance employed. By measuring the resistance of cylin- 

 ders of Laminaria in solutions of one salt and in solutions containing 

 two or more salts, he has brought forward much evidence as to the 

 penetration of ions into plant cells. While this method has yielded 

 very valuable results both as to the rate of entrance of ions and also 

 the total number of ions penetrating, it does not yield results which 

 give us a knowledge of the relative amounts of the various ions which 

 penetrate the tissue when the qualitative as well as the quantitative 

 relationships of the nutrient solution are varied. Osterhout has 

 shown, however, that penetration is more rapid, and the degree of 

 permeability is greatly increased, in unbalanced solutions and further 

 that as the permeability of the plant tissue more nearly approaches 

 normal the growth of the plant is also more nearly normal. 



Szucs 11 has used CucurMta pepo as an indicator by immersing the 

 young seedlings in various solutions for varying periods of time and 

 counting those still able to show geotropic movement when placed in a 

 horizontal position in a moist chamber. He found a marked antagon- 

 ism between copper sulphate and aluminum chloride and concludes 

 from his experiments that antagonism consists in the mutual hin- 

 drance of similarly charged ions in entering the cell. He states 

 further that the rate of absorption of equally charged ions is of great 

 importance. His chemical methods are open to question, for in the 

 experiments reported the test for copper used was that of boiling the 

 roots and testing the resulting solution for copper with hydrogen 

 sulphide. 



By analyzing the solution in which pea seedlings had grown, Pan- 

 telli 12 has determined ion absorption. The growing period was short. 



11 Jahrb. Wiss. Bot. (Pringheim), vol. 52, no. 1 (1912), p. 85. 

 ™loid., p. 211. 



