Oct. I, I92I Effect of Soil Temperature on Development of Nodules 2 7 



ference in the ratios and the consistent similarity of the curves can 

 hardly be explained otherwise than as a temperature effect upon nodule 

 development which is quite different from that upon development of 

 root or shoot. 



EFFECT OF SOIL TEMPERATURE UPON THE COMPOSITION OF THE 

 INOCULATED PLANTS 



In order that comparisons might be made of the amount of nitrogen 

 found in inoculated and uninoculated plants, total nitrogen determina- 

 tions were made of shoots, roots, and nodules of the plants grown in 

 each series. Since the uninoculated plants did not remain free from 

 nodules, the desired comparisons can not be made. Nevertheless the 



Od 



07 



\ 

 %.03 





sdQ. 





/O 



12 /S /a 2/ 24 27 30 33 3$ 



0£G7?£SS C£A^r/S7?^£>£ 



Fig. 4.— Ratios of weight of nodules to weight of tops and of roots. Second experiment. 



difference in nitrogen found were so marked in the series that the analyses 

 of one series, the last that was grown, is given. 



Table IV. — Percentage of total nitrogen found in shoots, roots, and nodules of soybean 

 plants grown at a series of soil temperatures in April and May 



Temperature 



°c. 



15 



18 



21 



24 



27 



30 



33 



36 



Nodules. 



5-95 

 6.95 

 6.25 



5-95 

 6.25 

 6.25 

 6. 00 

 5-70 



The greatest differences in content of nitrogen are found in the shoots, 

 the roots being very uniform and the nodules hardly less so. It will be 

 seen that, generally speaking, the high nitrogen content of the top is 



