286 IMPORTANT VARIETIES OF FISSION-FUNGI. 



At first sight, absence of production of pyocyanin and of 

 denitrifying action (very many cultures were investigated 

 in vain in these respects by Weissenberg) appear suffi- 

 cient to separate the organism from the Bact. pyocyaneum; 

 but this is not the case, for the following reasons: 



1. Ruzicka has also obtained Bact. fluorescens with 

 formation of pyocyanin. 



2. We and other writers have had cultures of Bact. 

 pyocyaneum which no longer produce any trace of pyocy- 

 anin, and Ruzicka has observed, in aerated cultures of 

 Bact. pyocyaneum, a marked reduction in the formation of 

 pyocyanin (possibly transformation into pyoxanthose?). 



3. Not only have Stutzer and Burri found a non-lique- 

 fying, fluorescent, denitrifying organism, but Kunnemann" 

 claims to have cultivated from the soil, besides a denitri- 

 fying Bact. pyocyaneum, also a denitrifying Bact. fluores- 

 cens (C. B. L. iv, 906). Most recently Kurt Wolf has 

 found the Bact. fluorescens to be frequently denitrifying 

 (H. R., 1899, ix, 538). 



4. The more restricted growth of the Bact. fluorescens 

 in the stab canal as compared to Bact. pyocyaneum may 

 be explained by acclimatization to higher temperatures; 

 thereby also the pigment produced by the fluorescens 

 takes on a bluer tone (Ruzicka). 



5. Also the difference that the Bact. pyocyaneum, 

 when introduced into the animal body, remains alive 

 there very well, while the Bact. fluorescens after three 

 days at the latest is dead, is not conclusive. 



In short, the methodic investigations of Ruzicka agree 

 absolutely with the impression which we obtained from our 

 most careful comparison of the cultures, and which we 

 advanced in the first edition. 



We have studied most minutely four different cultures 

 of the Bact. fluorescens isolated from water and soil. 



Microscopically we found rods which were partly plump, 

 and partly slender, with polar flagella. l Threads were rare- 

 ly wanting. In Plate 25, vm, a plump form is reproduced. 



It stains poorly or not at all by Gram's method. Upon 



1 We are not acquainted with the non-motile Bact. butyri fluores- 

 cens, Lafar (A. H. xm, 1), constantly present in Munich in butter. 

 It does not change the color of agar. 



