—_— Ss | 
— sh as. 
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.) gavethe 
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.68and69). Testsa 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 ses 
days at 11° C. to 13° C. 
The optimum temperature is, Bes 
roughly, 25° to 30° C. tee 
The maximum temperature is 34 uA 
to 35° C. (?) z. e., not determined ac- a 
curately but somewhere around this 
point. In October, 1905, eleven tubes ies 
of +15 peptone bouillon (stock 1622) 
were inoculated with the cucumber : 5 
strain (from acid bouillon?) and exposed \ / it 
in the thermostat for 5 days at 33° C. 
and lower, gradually rising to 36° C., % wees __ ft 
but most of the time under 35° C. (The ] 
thermostat was stable but the night 
temperatures were not recorded, only Se Rt aaa 
assumed to have been like the day tem- 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. Oct. 15, 5 p.m. 35050n6: 
6 p.m. 34-50°C. 9 p.m. 35.50° C 
9 p.m. 34.50°C. Midnight 35.50. CY 
12 p.m. 34.50°C. Oct. 16, 4 a.m. g6-G; 
Oct. 15, 4 a.m. 34.50°C. 6 a.m. 66.6. 
6 a.m. 34.50°C. II a.m. 389.50: Cy 
Noon 34.60°C. - 12:30 p.m. 35;80° C. 
*Fic. 92.—Growth of B. tracheiphilus in fermentation tubes: a, facultative anaérobically in cane-sugar bouillon, 
and, b, aérobically in meat-infusion with 1 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. 21, 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. 
