Studies of Bacillus Radicicola of Canada Field Pea 25 



The plants grown in nitrate-free solution with their roots exposed to 

 light were slightly shorter than, and did not have quite as many nodules 

 as, those grown in the same solution but with their roots kept in darkness. 

 In the presence of the nitrate the development of certain green algse 

 interfered somewhat with root growth. 



experiment 4 



influence of potassium nitrate and calcium nitrate in pfeffer's 



solution 



The procedure in this experiment was the same as in experiment 3. 

 Only one plant was grown in each cylinder. Calcium nitrate was replaced 

 by calcium chloride, and potassium nitrate was replaced by potassium 

 chloride. The plants were kept until they began to blossom. 



Results 



In the solution with the nitrates, two or three nodules developed on each 

 plant within twelve days after inoculation. No more nodules developed 

 after that. In the cylinders not covered with black paper, algse developed 

 in abundance, and, surrounding the roots, dwarfed the plants. In the 

 cylinders covered with black paper, also, some algae developed in time, 

 but they were far less abundant. 



In the nitrate-free solution there was an abundant development of 

 nodules. The nodules were more numerous on the plants grown in the 

 cylinders covered with black paper than on those the roots of which 

 were exposed to light. The root system of the plants grown in the nitrate- 

 free solution was more developed than that of the plants grown in the 

 nitrate solution. 



An interesting point observed in this experiment and in experiment 3 

 was that the nodules developed, both in the nitrate solution and in the 

 nitrate-free solution, immediately after inoculation. In the nitrate solu- 

 tion, however, no further development of nodules took place, while in 

 the nitrate-free solution there was a continual development of new. nodules 

 on the new rootlets as time went on. This would seem to indicate either 

 that the nodule-forming organisms were made inactive by the nature of 

 the solution, or that the solution in some way affected the resisting power 

 of the plants. 



