WILT OF CUCURBITS. 



293 



The organism produces little or no odor. I have never been able to detect any, but 

 the striped cucumber beetle seems to be able to do so. 



Successful transfers of this organism were made from cultures exposed for twenty 

 minutes to a very low temperature using a mixture of sulphuric ether and frozen carbon 

 dioxide ( 77 C.). At another time several experiments with liquid air ( 119 C.) gave the 

 same results, but quantitative tests showed the majority to have been killed. When exposed 

 in bouillon over night to the temperature of liquid air, poured plates showed about 65 per 

 cent of the organisms to have been destroyed (Vol. I, figs. 68 and 69) . Tests a half year later, 

 exposing in liquid air for half an hour, showed over 50 per cent to have been destroyed. 



The minimum temperature for growth is (?) 8 C. In peptone-water, inoculated and 

 kept in the ice-box at 6 to 10 C., there was no clouding for 16 days, but on removal to 

 room-temperature (25 to 26 C.) the 

 tube clouded thinly in 48 hours and 

 was subsequently used successfully for 

 the infection of plants (page 271). At 

 another time there was no clouding in 30 

 days at 11 C. to 13 C. 



The optimum temperature is, 

 roughly, 25 to 30 C. 



The maximum temperature is 34 

 to 35 C. (?) i. e., not determined ac- 

 curately but somewhere around this 

 point. In October, 1905, eleven tubes 

 of +15 peptone bouillon (stock 1622) 

 were inoculated with the cucumber 

 strain (from acid bouillon?) and exposed 

 in the thermostat for 5 days at 33 C. 

 and lower, gradually rising to 36 C., 

 but most of the time under 35 C. (The 

 thermostat was stable but the night 

 temperatures were not recorded, only 

 assumed to have been like the day tern- Fig. 92.* 



peratures.) All of the tubes remained 



clear during the exposure and none of them clouded when removed to room temperature 

 (25 C.). Two checks held at 25 C. clouded in 48 hours. This experiment was repeated 

 three days later, paying careful attention to the night temperatures. Twelve tubes of 

 bouillon were inoculated and exposed in the same thermostat for 44! hours, after which 

 they were removed and placed at 25 C. Two tubes were held as checks. The latter 

 clouded in 48 hours. The heated tubes never clouded. The recorded thermostat tem- 

 peratures were as follows : 



Oct. 14, 4 p.m. (after opening) 34. 10 C. 



6p.m. 34.5oC. 



9 P.m. 34.50C. 



12 p.m. 34-50 C. 



Oct. 15, 4 a.m. 34-5o C. 



6 a.m. 34-50 C. 



Oct. 15, 



Oct. 1 6, 



Noon 



34.6oC. 



5 P.m. 

 9 p.m. 

 Midnight 

 4 a.m. 



6 a.m. 

 ii a.m. 

 12:30 p.m. 



35.50C. 



35.50C. 



35.50C. 



36 C. 



36 C. 



35.5oC. 



35.8oC. 



*FiG. 92. Growth of B. Iracheiphilus in fermentation tubes: a. facultative anaerobicaily in cane-sugar bouillon, 

 and, b, aerobically in meat-infusion with i per cent dextrine. The dextrine used was readily soluble in water and did 

 net give a red reaction with iodine. Tube containing cane-sugar was inoculated Feb. 3, 1896, very copiously from 

 tube 4, Jan. 2 1 , a slant tube of sugar-agar inoculated from plant No. 246. The tube was doubtfully clouded in the open 

 end on Feb. 6, and plainly so on Feb. 7. On Feb. 8 it was thinly clouded in the whole of closed end but the fluid was 

 still alkaline. On Feb. 13 clouding was uniform in open end and closed end (nearly so on Feb. 10) and fluid was acid 

 to litmus. On this date a transfer to potato yielded a pure culture of B. tracheiphilus. On Feb. 27 culture was dead, 

 having been destroyed by its own acid. The dextrine-bouillon was inoculated May 8, 1895, and was clouded in open 

 end May 13 but clear in closed end. On May 18 it was still clear in closed end and fluid was alkaline to litmus. 



