Apr. IS. 1920 Effect of Solution Reaction on Germination and Growth 93 



(7) A reaction of 2.96 Pg is probably below the critical reaction for all 

 plants studied. 



(8) A reaction of 2.16 Pg caused the death of the seedlings of all plants 

 within a comparatively short time and was found to favor the growth of 

 molds in the cultures. 



(9) A reaction of approximate neutrality (6.97 Pg) was slightly less 

 favorable to alfalfa and decidedly less so to wheat, com, and soybeans 

 than a slightly acid reaction. 



(10) A reaction of 7.71 P^ produced further depression of growth 

 beyond that observed at 6.97 Pg except in the case of com seedlings. 



(11) The hydroxyl ion was apparently more harmful than the hydro- 

 gen ion in equivalent concentrations. 



(12) Measurements of reaction of solutions before and after the growth 

 of wheat seedlings showed a general tendency for the plant to adjust the 

 reaction toward a point slightly below neutrality. 



(13) The actual value of the change of reaction produced by the growth 

 of seedlings in a given culture was found to be a function of the stability 

 of the solution as indicated by the slope of the electrometric titration 

 curv'e at the point representing the composition of the solution. 



(14) No indication was obtained of any harmful effect of the monophos- 

 phate group, H2PO4, other than that produced by the hydrogen ion formed 

 through its dissociation. 



(15) Germination of the seed was found less sensitive to an acid reac- 

 tion in wheat, com, soybeans, and alfalfa than was the subsequent growth 

 of the seedling. 



(16) A reaction of 4. 1 1 Pg did not exert a depressing effect on the germ- 

 ination of any of the seeds studied. 



(17) A reaction of 2.96 Pg did not appreciably affect the number of 

 seeds germinating but considerably reduced the weight and apparent 

 vigor of the sprouts produced. 



(18) A reaction of 2.16 Pq did not prevent the formation of sprouts 

 except in alfalfa, but all sprouts produced were dead at the end of the 

 7-day germination period. This reaction induced the extensive growth 

 of molds upon the seeds. 



(19) The optimum reaction for the germination of the seeds of the five 

 plants studied is probably below 7.71 Pg and above 2.96 Pq, a slightly acid 

 reaction being found most favorable in all cases, 



LITERATURE CITED 



(i) BreazealE, J. F., and LeClerc, J. A. 



I912. THE GROWTH OP WHEAT SEEDLINGS AS AFFECTED BY ACID OR ALKALINE 



CONDITIONS. U. S. Dept. Agr. Bur. Chem. Bui. 149, 18 p., 8 pi. 

 (2) Cameron. F. K., and BreazealE, J. F. 



1904. THE TOXIC action of ACIDS AND SALTS ON SEEDLINGS. In Jour. Phys. 

 Chem., V. 8, no. i, p. 1-13. 



