148 



plate to bright sunlight for 3 hours destroyed nearl}' all of the organ- 

 isms. In that part of the plate which was not exposed the yellow 

 colonies came up thickly in 96 hours at 23^ C/ He does not speak of 

 having tried the result of shorter exposures. Russell and Harding 

 found that exposure of Ps. campestris in agar plates for 1.5 minutes to 

 an August sun (latitude 13°) destro3'ed IH) per cent of all the organ- 

 isms. Similar cultures exposed for 30 minutes to a November sun 

 remained entirely sterile.^ 



Resistance to Heat. 



Ps. JiyacintJu is quite sensitive to heat, much more so than the 

 bacterial parasites of the warm-blooded animals. To a less degree the 

 same is true of Ps. ])l\cmedi and Ps. canqjestrk. See Temperature 



relations. 



Resistance to Acids. 



Ps. hyacintJn is quite sensitive to acids, being restrained from growth 

 b}" comparatively small doses. It will tolerate more acid in a solid 

 than in a fluid medium, and more of some acids than of others. See 

 Malic acid gelatin and Sensitiveness to acids. In beef broth with 

 malic acid +30 appears to be about its limit of growth. 



Resistance to Alkali. 



Ps. hyacinthi will grow in —25 gelatin and in —20 beef broth, but 

 experiments have not been numerous enough to determine just how 

 much alkali it will endure. In gelatin and beef bouillon —30 of Ful- 

 ler's scale is probably al)out the limit of toleration of caustic soda. 



Growth in Presence of Calcium Sulphite. 



Ps. cam/pestris grew in 10 c. c. portions of galactose-peptone water 

 with addition of 10 milligrams of calcium sulphite, but growth was 

 distinctl}" retarded. The stock consisted of distilled water, \ per cent 

 peptone, and \ per cent galactose. Other organisms were not tested. 



Growth over Chloroform. 



This test was made hj adding 5 c. c. portions of c. p. chloroform to 

 10 c. c. portions of sterile alkaline beef broth in cotton-plugged test 

 tubes. The beef broth was stock 382,^ well adapted to the growth 

 of this organism. The chloroform settled at once to the bottom, but 



^ A Bacterial Disease of Sweet Corn. Bulletin 130. N. Y. Ag. Exp. Sta., Geneva, 

 N. Y., 1897, p. 434. 



2 A Bacterial Rot of Cal^bage and Allied Plants. Bulletin 65. Ag. Exp. Sta., Wis- 

 consin. Madison, Wis., 1898, p. 19. 



^1,320 grains minced lean beef and 2,000 c. c. distilled water in ice chest 24 hours. 

 Steamed, filtered, resteamed, added water to make fluid 2,640 c. c. Titrated and 

 found + 25. Added caustic soda to 0. A fermentation tube yielded 0.6 c. c. gas with 

 B. coli. No peptone added. 



