74 Martin J. Prucha 



4. In a full nutrient solution containing nitrates a few nodules may de- 

 velop immediately after inoculation, but a subsequent continual develop- 

 ment of nodules seems to be inhibited. 



5. No nodule development took place in nutrient solutions in which 

 the individual essential elements were omitted, except in the case of ni- 

 trogen. 



6. In sandy soil a moisture content of 20 to 40 per cent was more favor- 

 able for nodule development than lov\"er or higher percentages. 



7. The addition of KNO3, Ca(N03)2, NH4CI, FeClg KCl, or peptone to 

 sandy soil in the proportion of J gram of the salts to 300 grams of the soil, 

 air-dry, had an mhibiting effect on nodule development on Canada field 

 peas. The addition of MgS04, KH2PO4, Ca(H2P04)2, and tannic acid, 

 especially at the lower concentrations, in 300 grams of the soil, had a 

 beneficial effect on nodule development on Canada field peas. 



8. Nutrition markedly influences the morphology of the nodule or- 

 ganisms. 



9. The addition of 1 cubic centimeter or more of a normal solution 

 of HCl to 10 cubic centimeters of agar medium 334, 335, or 337 was in- 

 jurious to the vitality, and therefore to the infecting power, of the alfalfa- 

 nodule organism. The addition of 2 cubic centimeters or less of a normal 

 solution of NaOH to 10 cubic centimeters of each of the above media 

 seemed to be slightly beneficial to the vitality and the infectmg power 

 of this organism. 



10. The organism of Canada field peas produced no visible groT\"th in 

 medium 334 when the following substances were added: levulose 2 per 

 cent, phloroglucin 0.2 per cent, potassium oxalate 0.5 per cent, potassium 

 citrate 0.5 per cent, Witte's peptone 5 per cent, Merck's peptone 

 3 per cent. 



11. The organism multiplies readily in some soils and in various sub- 

 stances; as many as 10,000,000,000 organisms per gram developed in wheat 

 bran and in ground peas. 



12. The infecting power of B. radidcola of Canada field pea was not 

 affected after the organism had been kept on medium 335 for two 3'ears 

 and a half in the laboratory, the culture being transferred once each month. 



13. The mfecting power of the organism was not appreciablj' influenced 

 by the various media. All the cultures in which living nodule-forming 

 organisms were found at the time of trial produced nodules. 



