308 BACTERIAL DISEASES OF PLANTS 



in cup-like hollows. The margin of the smaller colonies is 

 entire, that of the larger ones is fimbriate. Thickly sown plates 

 are entirely liquefied in 2 days at 15° to 16°C. 



Peptonized +15 beef bouillon, if inoculated from young 

 vigorous bouillon cultures, clouds thinly in 6 hours and moder- 

 ately to heavily in 24 hours at 24° to 25°C. The growth is best 

 at the surface, where a fragile white pellicle forms. There is 

 no rim, and no pseudozoogloeae are formed. In two days there 

 are heavy clouds and a flocculent white precipitate which is 

 slimy and finally viscid. The medium becomes slightly greenish 

 and small crystals appear in the sediment. 



In acid bouillons, pseudozoogloeae may occur and the rods 

 become very short (spheroidal). 



In —17 beef bouillon both filaments and involution forms 

 were seen at the end of 2 weeks. 



A fragile white pellicle forms also on Fermi's solution and 

 Uschinsky's solution, and pseudozoogloeae occur in the latter. 



In Cohn's solution it grows without green fluorescence, rim, 

 or pellicle, but with the formation of large feathery crystals. 



The organism blues litmus milk in well-defined strata 

 from the top downward; no acid is formed, the cultures being 

 dark blue by reflected light even after 6 months. 



The color-changes in milk likewise proceed from the top 

 downward in definite layers. In 15 to 20 days the whole tube is 

 3^ellow with a greenish tinge; it is translucent but without de- 

 struction of the fat or separation of whey and curd. In 4 months 

 when evaporated from 10 cc. to 5 cc. the milk is reddish brown 

 and rather thick. 



The organism is a cool-weather parasite. Its optimum 

 temperature is 24° to 25°C., its maximum (in bouillon and on 

 agar) is 29°C., and its minimum below 0°C. Of 20 bouillon 

 cultures exposed for 10 minutes at 47°C. none grew; of 12 bouil- 

 lon cultures exposed for 10 minutes at 46°C., one clouded after 

 11 days; exposure of bouillon for 10 minutes at 45°C. killed the 

 bacteria in some of the tubes (less than one-half) and retarded 

 development in the others 3 to 5 days, i.e., many were killed; 

 finally, exposure in beef bouillon for 3>^ days at 33° to 36°C. 

 destroyed the organism, i.e., prevented subsequent clouding at 



