283 



The very common presence of B. polymyxa in the bark of the 

 nodules of the Legnminosae is certainly also a direct consequence of 

 its pectinase production. Its presence there is of so general occni-ience, 

 (liat it reminds more of symbiosis than of saprophytisni. In the 

 bacteroïdal tissue B. polymyva is however completely absent. 



Properties of the colonies. 



The colonies on agar as well as those on gelatin are characteristic. 

 On malt-wort gelatin they resemble at first thin, watery, sideways 

 quickly extending, slowly liquefying layei'S, which by and by 

 become deeper and cloudy by their strong growth. At length the 

 gelatin is completely liquefied and then these cidtures resemble those 

 of common hay bacteria. On malt-wort agar there is a profuse produc- 

 tion of slime, whence very distinct voluminous and wrinkled 

 colonies appear. The slime attracts part of the pigment from the 

 wort-agar thereby becoming brown-coloured, which gives a character- 

 istic appearance to the colonies. 



On glucose-kalium-phosphate-ammoninm-phosphate-agar they be- 

 come glass-like transparent, somewhat resembling glass globules, so 

 peculiar that at estimating the numbei- of germs in soil samples, they 

 may directly be recognised and counted. Silica plates, saturated with 

 food, also produce such drop-like colonies from soil. Some varieties form 

 n)uch less slime than others and this slime is either tough or soft. 



Microscopically those with saft slime consist of much shorter 

 rod lets. Hence, one is at first disposed to think of different species, 

 but further research shows the similarity, which is the more con- 

 vincing, when beside the natural varieties, the mutation phenomena 

 in the pure cultures are studied. On cane-sugar-asparagine agar 

 many colonies, at first quite homogeneous and soft, when getting 

 older produce small, rather solid, transparent, secundary colonies 

 which, after separation from their suriounding (which is not easy) 

 prove to be constant. On malt-wort agar the variety with tough 

 slime, when growing older produces extensive, flat secundary colo- 

 nies, showing a hereditary loss of the factors for slime formation. 



In liquid nutritive media the form resistent to high concentrations 

 of the food gives remarkable cultures. 



In a malt-wort of 10° Balling at 30° they consist of excessively 

 voluminous slime masses, forming after one or two weeks a thick, 

 coherent, floating film, inflated by carbonic acid, whilst no hydrogen 

 is detectable. Only in the anaerobic butylic fermentation something 

 of the like may be observed but then much hydi-ogen is present. 



