200 



BACTERIA IN RELATION TO PLANT DISEASES. 



but afterwards excellent; produces a brown stain in host, on agar, gelatin, etc.; pigment 

 soluble in water and glycerin; streaks on silicate jelly (with Fermi's solution) feeble at 

 end of sixth day (25 C.) ; grows readily on steamed potato cylinders, producing a pale 

 brown to dark brown stain and an alkaline reaction ; odor on potato feebly disagreeable ; 

 has slight action on potato starch ; slowly converts milk into an alkaline translucent fluid ; 

 gradually changes the lilac color of litmus-milk to a deep indigo or hyacinth blue ; litmus- 

 lactose-agar slowly becomes a deeper blue; slight reducing power on litmus; aerobic; reduces 

 nitrates to nitrites ; portion of rods killed by freezing, others retain vitality and motility ; 

 injured by acids (Hunger, EFS.) ; thermal death-point 52 C, approximately; minimum 

 temperature io C, approximately; optimum 37 Cor below; maximum 41 C, approxi- 

 mately; alive in milk after 48 

 days; browned growths are 

 usually dead; dies early on 

 steamed potato, usually the first 

 or second week. Chains occur 

 (Honing, p. 247). 



Group No. 21(^.3333823. 



NEGATIVE. 



Spore-formation ; capsules ; 

 long chains and filaments (so 

 far as observed) ; liquefaction 

 of gelatin (at least during first 

 weeks) , blood-serum ; starch-de- 

 struction (or feeble) ; precipita- 

 tion of casein from milk; acid 

 from milk; gas-formation (all 

 media) ; anaerobism (so far as 

 known) ; acids from sugars and 

 alcohols (so far as known) ; 

 dendritic growth; green fluo- 

 rescence; vile odors; wrinkled 

 growth on potato; disintegra- 

 tion of cooked potato-cylinders ; 

 action on pigment of dilute acids 

 (10 per cent) and alkalies (5 per cent) ; pigment insoluble in ethyl alcohol (absolute), sul- 

 phuric ether, chloroform, turpentine, benzine, xylol, benzole, carbon bisulphide; cultures 

 not viscid, or only exceptionally and slightly so ; growth in Cohn's solution absent or feeble ; 

 Gram's stain; indol. Non-motile (Hutchinson). 



Any organism which produces spores, stains well by Gram, gives a decided pink reaction 

 in old peptone-water cultures with sulphuric acid and sodium nitrite, evolves gas, liquefies 

 gelatin readily, acidifies cream-free milk, develops a lab ferment, grows abundantly in Cohn's 

 solution, grows well anaerobically in bouillon with grape-sugar or cane-sugar, has a thermal 

 death-point above 53 C, or fails to blue (cream-free) litmus milk and to brown steamed 

 potato on long standing, may be set down at once as something else. 



This organism may be distinguished horn Bacillus phytophthorus and its allies by the fact 

 that it does not liquefy gelatin, at least for several weeks, does not redden cream-free litmus 



Fig. 112.* 



*FlG. 112. Colonics of Bacterium solanacearum on +15 standard nutrient agar after 8 days at 23 to 27 C. 

 Plate poured June 18, k>i 13, from the interior of a diseased tomato stem, received from South Carolina. Natural si/e. 



