iqiq] DRECHSLER— ACTINOMYCES 



159 



ment rapid; nutritive mycelium dark brown or greenish brown; 

 aerial mycelium profuse, changing from white to violet or pinkish 

 gray; guttation profuse; tyrosinase reaction moderate. 



Morphology. — In this species the characteristic development 

 consists in the prohferation of a number of long branches in an 

 irregular whorl from a long and somewhat thickened axial filament. 

 Secondary branching is common, but usually more or less remote. 

 Vacuoles associated with h>phal distensions are found in the axial 

 filaments and in the main branches, and metachromatic granules 

 occur abundantly in many of the older sterile hyphae (fig. 91). 

 The long cyhndrical spores, 0.6-0.7X1.0-2.0/1, are formed by 

 the septation of sporogenous h>'phae that terminate in open, 

 sinistrorse spirals of 2-3 turns, 4.0-5.5 y, in diameter, followed by 

 the sphtting of the septa along a median plane, and the separation 

 of the two halves by a contraction of the dehmited protoplasts. 

 The progress of sporogenesis is usually basipetal, but not infre- 

 quently the first divisions may result in a number of segments of 

 varying lengths, which by subsequent divisions are reduced to the 

 magnitude of the ultimate spores. 



Isolated once from soil collected in Cambridge, Massachusetts. 



ACTINOMYCES XVII 



A. scabies (Thaxter) Giissow (6) 



Morphology. — The aerial mycehum of this species, which is 

 one of the largest of dextrorse forms, consists of long prostrate 

 filaments on which lateral branches are inserted at short intervals. 

 Secondary branching is abundant and usually associated with a 

 successive order of development (figs. 93a7-aj). The more or 

 less cylindrical spores, 0.8-0.9X1 3-1 .5 m, are developed from 

 dextrorse spiral hx-phae of 3-14 turns, 2 .0-3 . 5 m in diameter, by the 

 insertion of conspicuous septa and their subsequent sphtting along 

 a median plane. In many h>phae the septa before their division 

 can be seen to occupy a transverse equatorial position in the pecuHar 

 spherical structures to which reference has been made elsewhere, 

 and which here occupy slight but perceptible hyphal distensions 

 (figs. 92, 93///, 93/^2, loicy). Whenever the spherical structures 



