Studies of Bacillus Radicicola of Canada Field Pea 15 



small colonies was introduced into 5 cubic centimeters of sterile water in 

 a test tube, and from this infusion a number of petri dishes of different 

 dilutions were again prepared. From one of the colonies that developed 

 on these petri dishes a transfer was made on agar slope with medium 335. 

 This culture was used in all the experiments except experiment 11. The 

 stock culture was kept on a shelf in the laboratory, and consequently 

 was exposed for nearly three years to diffused light and to the ordinary 

 variations ot temperature and other atmospheric changes. The trans- 

 ferring of the stock culture was made at irregular mtervals of time varying 

 from one to three months, and the cultures were kept in test tubes on 

 agar slopes of medium 335. 



identification of the organism 



In order to be certain that the organism isolated was the causal organism 

 of the nodules on Canada field peas, the following procedure was followed : 

 (1) Canada field peas were grown under sterile conditions and were inoc- 

 ulated with this organism; (2) from one of the nodules that developed 

 under sterile conditions a culture. No. 2, was isolated by the same method 

 as described above; (3) the original culture and the culture No. 2 were 

 again tested as to their ability to cause the development of nodules on 

 Canada field peas under sterile conditions; (4) the two cultures were 

 compared m the laboratory with respect to their morphological characters 

 and physiological activities. 



Ten Canada field peas were grown under sterile conditions according to 

 the method described on page 13, one plant in each of ten glass cylinders. 

 Five of the plants were inoculated with the above organism, and five 

 were left without inoculation, as controls. At the end of six weeks the 

 plants were examined. They had made a fair growth, having reached a 

 height of 60 centimeters. They were spindling, however, the leaves were 

 small, and the root system was very poorly developed. All the inoculated 

 plants had nodules on their roots, while the controls were free from any 

 nodules. Each plant and the soil in which it was grown were examined 

 for contamination. One of the controls was found to be contaminated 

 with a mold, and one of the inoculated plants was contaminated with a 

 yellow organism. Four of the controls were sterile, and four of the in- 

 oculated plants were found to be sterile with respect to organisms other 

 than B. radicicola. 



