342 Journal of Agricultural Research voi. xvi, no. 12 



Action on milk. — Digestion without previous coagulation. 



Production oif indol. — Statements in the literature are discordant. 

 A number of different strains of Ps. fluorescens have been tested here 

 for indol production, a feeble or moderate reaction having been obtained. 

 The test is not considered to have much significance. 



BRIEF SUMMARY OF CHARACTERISTICS OF TYPICAL PSEUDOMONAS 



FLUORESCENS * 



In the following summary the characteristics written within paren- 

 theses apply to typical cultures only (including the strain studied by 

 Bright); the other characteristics apply not only to typical cultures but 

 to all the cultures studied of the fluorescens type — (that is, type 2, p. 337). 



Morphology: Short, lophotrichic, Gram-negative rods about 0.6 m in diameter. 

 No spores. 



Growth on agar: Soft, smooth, with greenish fluorescence if conditions are 

 favorable. 



Gelatin colonies: (Large), liquefied (center structureless), edges entire. 



Relation to oxygen: Strictly aerobic. 



Ammonia produced from organic nitrogenous matter. 



Acid production from dextrose and sucrose, but not from lactose or glycerin. 



Nitrates reduced to nitrite (in peptone media containing no nitrogen except 

 the nitrate). 



DiASTATic ACTION ON STARCH: Weak or none. 



Milk digested without coagulation. 



PSEUDOMONAS CAUDATUS 



Pseudomonas caudatus (Wright), {33, p. 444) Conn has been recognized 

 by the writer for a number of years and has been mentioned in previous 

 publications (5, 7-1 1), but not named. It is now believed to be 

 identical with Bacillus caudatus Wright. Earlier surveys of water 

 bacteria by Frankland {17), Tils {50), and Zimmerman (54) contain 

 descriptions of orange or yellow liquefying bacteria, but they are either 

 meagerly described or else show marked differences from the organism 

 studied here. The identification Avith Wright's organism is based pri- 

 marily upon a color plate shovnng the gelatin colony and upon his 

 description of the morphology. He describes the morphology of the 

 organism as follows {53, p. 444) : 



A rather small, slender, nonmotile bacillus, with conical ends, occurring often in 

 pairs and in longer forms, sometimes threadlike, which may show irregular segmen- 

 tation; no spore formation observed. 



His illustration of the colony agrees well with the present organism as 

 to structure and agrees as nearly vdth the shade of orange observed as 

 could be expected in a colored plate 20 years old. Although Wright 

 does not give the size of the organism in exact figures and calls it immo- 

 tile, there is little question as to its identity. 



Morphology. — Ordinarily the organism is a very slender rod, so small 

 that its diameter is difficult to measure with the ordinary microscope. 



