118 CROWN-GALL OF PLANTS. 



in the — 15 tubes only. This experiment was several times repeated, 

 with the same results. 



Afterwards the organism was tested in —16 peptonized beef 

 bouillon and in —34, with the following results: In the — 16 the old 

 strain (now nonvirulent) made a copious growth, and a more recently 

 isolated virulent strain made a slight growth (about one-twentieth as 

 much as the preceding). In the —34 the recent isolation made no 

 growth, and the old strain (B) about one-twentieth as much growth 

 as it did in the — 16. 



OPTIMUM REACTION FOR GROWTH IN BOUILLON. 



The optirnum reaction appears to lie between +12 and +24 on 

 Fuller's scale. The first tests were made in May, 1908. Subsequent 

 experiments (1910) gave the confirmatory results detailed in Table I, 

 from which it appears that the organism is able to overcome moderate 

 alkalinity and grow vigorously down to on Fuller's scale. Judging 

 from these results, the optimum (sodium hydroxid) alkalinity for 

 growth in peptonized beef bouillon lies between -1-12 and -f24 on 

 Fuller's scale, and the limits for growth between —16 and some 

 undetermined point between -f24 and +34, the tubes being inocu- 

 lated soon after the final titrations but left exposed at room tempera- 

 ture to the COj of the air. 



213 



