THE GENUS RHODOCOCCUS 245 



who noted the property of nitrate reduction. We may 

 use Flugge's name, with credit to Dyar's emendation, for 

 the first type of Rhodococcus. 



1. Rhodococcus roseus (Fliigge, Dyar) Winslow. A 

 saprophytic coccus, found most commonly in earth, water, 

 and air. Occurs in pairs, groups, or packets. Generally decol- 

 orizes by Gram. Abundant, red surface growth. Reaction in 

 dextrose broth faintly acid, in lactose broth alkalin or faintly 

 acid. Gelatin either not liquefied or liquefied very slowly. 

 Nitrates reduced to nitrites, but not to ammonia. 



The second type among the rhodococci is distinguished 

 by failure to attack nitrates. Ten of our strains fell under 

 this head. Five of the ten showed packet formation, and 

 none liquefied gelatin within two weeks. In other respects 

 these strains showed the characters noted above as typical 

 for the genus. The non-nitrate-reducing type may per- 

 haps best bear the name given by Cohn (1875) to a 

 coccus which formed a rust-red growth on horse dung in 

 the laboratory. The type may be defined as follows: 



2. Rhodococcus fulvus (Cohn) Winslow. A sapro- 

 phytic coccus, found most commonly in earth, water, and air. 

 Occurs in pairs, groups, or packets. Generally decolorizes by 

 Gram. Abundant, red surface growth. Reaction in dex- 

 trose broth faintly acid, in lactose broth alkalin or faintly 

 acid. Gelatin either not liquefied or liquefied very slowly. 

 Nitrates not reduced. 



To which of these types the published descriptions of red 

 cocci refer, it is generally impossible to say, since data 



