KEY TO GENUS BACTERIUM. 199 



bluish-green fluorescent pigment diffuses out from the culture, l both in 

 gelatin and agar. 



All varieties are provided with a single flagellum or a bunch of 

 flagella located at the end. The group consists of varieties very 

 closely related to each other, none of which forms gas from sugar. 

 According to Zimmermann, all fluorescent bacteria, when young, 

 stain by Gram's method ; but according to our observations, they do 

 not do so regularly. 



( A ) Gelatin liquefied. Colonies in plate, after liquefaction begins, 

 are surrounded by hairs. 



(a) Intense production of pigment, usually bluish-green, upon 

 all nutrient media, also in milk and bouillon. Milk coag- 

 ulated with alkaline reaction ; then coagulum is dissolved. 

 Pathogenic for animals. Bact. pyocyaneum (Fliigge), 

 L. and N., page 281. 



(/5) Pigment production less ; in bouillon very slight. Milk 

 not coagulated ; later it becomes clear and colored greenish- 

 yellow. Bact. fluorescens (Fliigge), L. and N., page 

 285. 



(B) Gelatin not liquefied. Colonies in plate, even-bordered, 

 wavy, reminding one of the Bact. coli. 



(a) Growth on agar and gelatin, white or yellow. No formation 

 of blue or brown pigment aside from the fluorescent mate- 

 rial. Bact. putidum (Fliigge), L. and N., page 287. 

 (/3) Besides the fluorescent pigment, there is also formed a 

 blue, deep blue, or dark brown pigment in varying amount. 

 Grape-sugar milk becomes blue to bluish-gray. Bact. syn- 

 cyaneum (Ehrenb. ), L. and N., page 289. 



VI. The bacterial growths are pale (white to brownish colored], and 

 through diffusion the surrounding nutrient medium is colored intensely 

 brown. 



1. Gelatin not liquefied. Bact. brunificans, L. and N., page 



292. 



2. Gelatin liquefied. Bact. ferrugineum (Rullmann), L. and N., 



page 292. 



II. COLONIES UPON THE NUTRIENT MEDIA ARE ROUNDISH AT THE 

 BEGINNING ONLY, IF AT ALL ; LATER, THERE EXTEND MORE 

 OR LESS FROM WITHIN OUTWARD, RAY-, FORK-, BAND-, OR 

 SAUSAGE-LIKE OUTGROWTHS. 



In the Bact. vulgare, where these outgrowths may be absent, one 

 observes best in 5%-Q% gelatin a swarming in the periphery of the 

 colonies in the plate. In the gelatin stab culture there sometimes 

 occurs the formation of branches. (Genus : Proteus Hauser. ) 

 (a) With spontaneous motion and peritrichous flagella. 



1. Gelatin not liquefied. Branching very beautifully developed. 



Causes putrid decomposition. Bact. Zopfii (Kurth.), L. 

 andN., page 29.3. 



2. Gelatin usually liquefied. No branching. Causes intensely 



1 For transition forms between these varieties, consult the detailed 

 descriptions. 



