I9I9] DRECHSLER— ACTINOMYCES 151 



Identity with A . lavendulae established by comparison of cultural 

 and morphological characteristics. 



MoRPHOLOGY.^ — The mycelium consists of long prostrate axial 

 filaments, branching rarely except at the end. Sporulation is 

 usually initiated at the tip of the filament, and proceeds basipetally 

 by the insertion and transformation of almost invisible septa, to 

 the point of attachment of the first sporogenous branch (figs. 10, 1 1). 

 The sporogenous branches are rarely crowded, although at the base 

 of the sporogenous axial termination an opposite arrangement is 

 not uncommon. Secondary branching occurs frequently; septa 

 are entirely absent, except when associated with the progressive 

 basipetal delimitation of spores. 



The sporogenous hyphae terminate in dextrorse, moderately 

 compact spirals of 4-12 turns, 2 .0-3 .8 /^ in diameter. The spores 

 are ellipsoidal, with nuclei not readily demonstrable. Metachro- 

 matic material occurs abundantly in many old hyphae (fig. 15). 



Isolated 3 times from soil collected in Cambridge, Massachusetts. 



ACTINOMYCES IV 



Cultural characters. — On glucose agar, nutritive myceHum 

 colorless; aerial mycelium moderately profuse, velvety in appear- 

 ance, changing from white to smoky blue; no guttation. On 

 potato agar, tyrosinase reaction vigorous; aerial mycelium first 

 produced white, not subsequently much discolored, becoming 

 matted to the substratum as a result of excessive guttation, and 

 later completely overgrown by a loose growth of smoky blue 

 secondary mycelium. 



Morphology. — The sporogenous branches with dextrorse 

 spirals of 2-12 open turns, i .5-2.5 ix in diameter, are attached to 

 the long axial filaments usually at wide intervals, in a loose race- 

 mose arrangement. Secondary branching, although rare, occurs 

 occasionally, and is then associated with simultaneous sporulation 

 (fig. 18). Development of the 1-2-nucleated spores, o . 7-0 .8X0.9- 

 1.1 IX, proceeds by the insertion of conspicuous septa, followed by 

 their constriction and subsequent conversion to hyaline isthmuses 

 (figs. 7oa-e). Two germ tubes are usually produced, of a more or 



