72 



Martin J. Prucha 



TABLE 18 (concluded) 



Laboratory number of culture 



Culture 

 medium 



Age of 

 culture 



(days) 



Average 



number 



of nodules 



per plant 



Number of 



living 

 organisms 

 in culture 



11 



400 

 400 

 400 

 400 



310 

 310 

 310 

 310 

 310 



300 

 400 

 310 



98 

 105 

 110 

 115 



15 

 49 

 61 

 81 

 105 



15 

 15 

 15 



0.5 

 



0.6 

 



6.2 

 7.8 

 



10.7 

 10.7 



7.1 

 7.1 

 5.2 



90,000 



9 







6 







3 







26 



3,240,000,000 



22 



8,000,000 



18 







15 



540,000,000 



10 



144,000,000 



27 



180,000,000 



28 



972,000,030 



29 



1,152,000,000 







The organism had been propagated and kept on medium 335, a non- 

 nitrogenous medium, for over two years before this experiment was started. 

 Several tests of infecting power were made during that time. This me- 

 dium was used also in experiment 12. As far as could be judged by all 

 these tests, the infecting power of the organism remained constant when 

 propagated and kept on this m.edium. Therefore the results shown in 

 experiment 13 as to the infecting power of the cultures on medium 335 

 are taken to represent the normal infecting power of the organism, and 

 serve as a basis for comparison of the infecting power of the cultures on 

 the other media. 



Of the seven cultures on medium 300, a nitrogenous medium, three 

 cultures — namely, 20, 24, and 27 — produced nodules. Cultures 24 and 

 27 were fifteen days old and culture 20 was forty-nine days old. The 

 organisms in cultures 20 and 24 were under the influence of medium 300 

 for one hundred and fifteen days, and culture 27 for only fifteen days. 

 These three cultures appeared as effective as those on medium 335. The 

 remaining cultures on medium 300 were from eighty-one to one hundred 

 and fifteen days old and did not produce any nodules, apparently having 

 lost their power of mfection. 



Similar results were obtained with the nitrogenous medium 400. Of 



