546 Bulletin 167 



of unabsorbed oxygen during the first hours of the experiment-. 



12. Fluorescence. — The fluorescing property was possessed 

 by the strains in varying degrees. Some were never observed 

 to fluoresce with the intensity which was typical of others. The 

 degree of fluorescence was also variable with the same strain 

 upon different media. Strain CXV was never more than 

 doubtfully fluorescent, but it was included in the studies for 

 comparative purposes with the idea that its ability to fluoresce 

 might be intensified by proper cultural methods. This result has 

 not been obtained, however, and for this and other reasons it is 

 probable that the organism in question should not be included 

 with the fluorescent group. 



The strongly fluorescent strains in general were the rapid 

 liquefiers and digesters, and they produced more ammonia than 

 the weakly fluorescent ones (c. f. chart page 551). Addition of 

 ammonia or sodium hydroxid generally brought out a bright yel- 

 low-green fluorescence in all vigorous cultures deficient in this 

 respect, with the exception of those of strain CXV (31). The 

 pigment disappeared in all cultures if made slightly acid, only 

 to reappear as soon as a slight excess of alkali was present. 

 In general upon agar and broth a beautiful yellow-green fluores- 

 cence appeared in from three to five days. On gelatin, fluores- 

 cence developed only to a slight degree. 



The green fluorescent pigment. — The most extended in- 

 vestigations concerning the pigment formed by the fluorescent 

 bacteria have been made by Gessard (9), Thumm (.31). and 

 Jordan (14 and 15). Gessard concluded that B. pyocyaneas 

 produces two pigments, pyocyanin and fluorescine. In order 

 to bring out clearly the nature of the fluorescent pigment the 

 papers of Thumm and Jordan (14) are quite extensively cited. 



Thumm studied the following species : 

 B. Iluorescens tenuis. 

 B. tluorescens putidus. 

 II. Iluorescens albus. 

 B. Iluorescens erythrospoms. 



