158 BOTANICAL GAZETTE [February 



ACTINOMYCES XIV 



Cultural characters. — On glucose agar, nutritive mycelium 

 usually colorless, but frequently becoming deep brown or black; 

 aerial mycelium consisting of a dense velvety weft, first white, later 

 changing to a creamy yellow. On potato agar, growth similar; 

 tyrosinase reaction absent. 



Morphology." — This species is characterized by the production 

 of extensive prostrate fructifications through the proliferation of 

 numerous lateral branching processes from long axial filaments 

 (figs. 76, 79, 81). A septum is occasionally present immediately 

 above the attachment of a branch, but more frequently is absent. 

 Secondary ramifications, resulting in more or less complex elements, 

 take place without reference to the stage of sporogenesis in the 

 proliferating branch. The elHpsoidal uninucleated spores. 0.5- 

 0.7X0.8-1 .2 /x, are derived from sinistrorse spiral h>phae of 

 1-8 turns, 2 .0-4.0 n in diameter, by the insertion and transforma- 

 tion of relatively thin septa, or without the appearance of demon- 

 strable septa. 



Isolated 4 times from soil collected in Cambridge, Massachusetts. 



ACTINOMYCES XV 



Cultural characters. — On glucose or potato agar, nutritive 

 mycelium opalescent; aerial mycelium first white, becoming only 

 slightly discolored with age; tyrosinase reaction moderate. 



Morphology. — Microscopically this species closely resembles 

 Actinomyces IV, differing from the latter chiefly in the abundant 

 proliferation of branches of the second or of a higher order. The 

 lateral elements thus formed follow the successive t>pe of develop- 

 ment (figs. 82, St,). The uninucleated spores, 0.7X0.9-1 .0 ju, 

 are formed from dextrorse spiral hyphae of 3-12 turns, i . 8-2 . 5 m in 

 diameter, by the constriction of conspicuous septa, and their trans- 

 formation into hyaline isthmuses. 



Isolated twice from soil collected in Manhattan, Kansas. 



ACTINOMYCES XVI 



Cultural characters. — On glucose agar, growth very meager; 

 never producing an aerial mycelium. On potato agar, develop- 



