Apr. 15, 1920 Effect of Solution Reaction on Germination and Growth 8 1 



probable that the depression in growth found in cultures i and 2 was 

 due to the physiological effect of their reaction upon the wheat seedlings. 

 The results obtained from this series do not give accurate data con- 

 cerning the effect of reaction upon the growth of wheat seedlings over 

 the entire range investigated. It seemed well, however, to include 

 them in this report on account of their bearing upon a large amount of 

 investigative work showing the ability of bacteria and fungi to compete 

 with higher plants for inorganic nitrogen if supplied with a proper source 

 of energy and carbon in the form of organic matter. This power of micro- 

 organisms has been demonstrated by numerous investigators under both 

 solution and soil-culture methods. For a more complete discussion 

 and an extensive bibliography on this subject the reader is referred to 

 the publication of Doryland (4). 



/oo 



90 



^ SO 



\30 



20 



/O 



O 



2 3 4^6 7 G 



Reaction as P^ 



Fg. 4. — Graphs showing the relation of growth of wheat, soybean, com, and alfalfa seedlings to reaction 



in series B. 



SERIES B 



On account of the difficulties arising from bacterial infection when 

 citric acid was employed in the cultures, further work was confined to 

 solutions having the composition given for series B. Wheat, soybeans, 

 corn, and alfalfa seedlings were grown, all cultures being duplicated in 

 the wheat, corn, and alfalfa series and quadruplicated in the soybean 

 The numbers of seedlings grown in each culture were as follows: 



series. 



wheat, 12; soybean, 6; corn, 4; alfalfa, 20. The following periods of 



