88 Journal of Agricultural Research voi. xix, no. 2 



approximately enough alkali was used just to neutralize the first hydrogen 

 ion of the H3PO4 molecule. The concentration of the monophosphate 

 group was undoubtedly higher in this culture, therefore, than in any 

 others of the series, since all the phosphorus present existed as the equiva- 

 lent of monosodium phosphate. In the cultures below No. 4 an increas- 

 ing part of the phosphorus exists as H3PO4, while in the cultures above 

 No. 4 an increasing amount exists as sodium phosphate (Na2HP04). 



THE EFFECT OF REACTION ON GERMINATION 



The effects of acids and alkalies upon the germination of seeds have 

 been studied by Promsy {22, 2j), Micheels {16, ij), and Plate {21). The 

 general conclusions can be drawn from these investigations that a 

 slightly acid reaction is favorable to the germination of most seeds, 

 while bases exert an injurious effect. The relation of germination to 

 acidity varies considerably with seeds of different plants and with the 

 acid used, organic acids being apparently more favorable than inorganic 

 when used in equivalent amounts. This is probably due to their lower 

 dissociation. Promsy found that the optimum concentration of acids 

 ranged from 0.5 to 5 parts per thousand, depending upon the nature of 

 the seed and the acid employed. Higher concentrations of acid inhibit 

 or prevent germination. It is asserted that the effects of acids and bases 

 on germination are a result of their favorable or unfavorable influence 

 on the enzymic processes concerned. 



The authors are not familiar with any work showing the effect of reac- 

 tion on germination in which hydrogen-ion or hydroxyl-ion concentra- 

 tion is taken as a measure of the reaction, or with any work showing the 

 relative sensitivity of germination and of the subsequent growth of the 

 plant to reaction so determined. Breazeale and LeClerc (i), in explaining 

 some of their results obtained in the growth of wheat seedlings in acid 

 cultures, draw the conclusion that the depressant effect of acidity is 

 greater during germination than in the subsequent growth of the plant. 

 They explain this by assuming a high sensitivity of the enzyms con- 

 cerned in germination, particularly the oxidases and peroxidases, to the 

 acid condition. From a practical standpoint it would seem desirable to 

 know to what extent the effects of soil acidity are due to its injurious 

 influence on germination and to its effects on the subsequent growth of 

 the crop. Numerous instances have come under the authors' observa- 

 tion in which seed planted in soils of high acidity apparently germinated 

 normally but either ceased to grow or died after the plants had attained a 

 small growth. This would indicate a condition opposite to the conclusion 

 of Breazeale and TeClerc (j). 



To investigate this point seeds of wheat, corn, soybeans, alfalfa, and 

 red clover were germinated in solutions having the same nutrient com- 

 position and reaction as those used in the growth of seedlings in series B. 

 The seeds were germinated upon pads of three ashless filters placed in Petri 



