212 Nitrogen Fixation— Symbiotic 



The mechanism of root infection by the legume organism was 

 studied in detail by Prazmowski in 1889. The amounts of nitrogen 

 obtained by the association of the plant and the bacterium were 

 worked out by Schloesing and Laurent. Leguminous plants were 

 grown in sterile glass cylinders containing sterile sand and watered 

 with sterile water. The composition of the gas in the cylinder was 

 determined. It was found that the uninoculated plants showed a 

 gain of only 0.6 mg of nitrogen and no nodule formation; the inocu- 

 lated plants, however, showed a gain of 34.1 and 40.6 mg of nitro- 

 gen and abundant nodule formation. These results were confirmed 

 by numerous investigators. It is sufficient to cite those obtained by 

 Virtanen (Table 47). 



Table 47. Gkowth of Red Clover lv Quartz Sand (from Virtanen) 

 pYL 6.5; 10 plants in eadi pot; age of plant.s, 106 days. 



Different plants vary greatly in the amount of nitrogen fixed, as 

 .shown by Wilson (Table 48). 



T.\BLE 48. Daily Uptake of Nitrogen by Various Leguminous Plants 



(from Wilson) 



