150 A MANUAL OF THE PENICILLIA 



initials more abundantly; conidiophores arising as short branches from 

 aerial hyphae, smooth- walled, mostly 20 to 35m by 2.0 to 2.8m, often shorter 

 and rarely longer than 50 or 60m; penicilli consistently small, simple; sterig- 

 mata rarely more than 4 or 5 in the verticil, commonly irregularly arranged, 

 often occurring in pairs or singly, variable in size, mostly 7 to 12m by 2.2 to 

 3.3m when borne in clusters, up to 20 to 25m by 3.0 to 3.5m when arising 

 singly, showing some tendency to be wedge-shaped but narrowing abruptly 

 to conspicuous conidium bearing tubes; conidia globose to subglobose, oval 

 or somewhat pyriform with comparatively heavy, smooth walls, varying 

 greatly in dimensions (fig. 42A), mostly 4.0 to 6.0m in diameter but ranging 

 from 3.0 to 8.0m, borne in very short divergent chains, consistently larger 

 in some chains than in others and with terminal conidia generally larger 

 than younger conidia in the same chain. 



Colonies on steep agar growing as on Czapek but less deeply furrowed 

 and producing abundant perithecia largely near the colony surface, ripening 

 within 10 days to 2 weeks. 



Colonies on malt agar spreading broadly, attaining a diameter of 6 cm. 

 in 2 to 3 weeks, plane, occasionally zonate (fig. 41B), growing margin 0.5 to 

 1.0 cm. wide, white to light flesh colored, central area in shades near avel- 

 laneous from the abundant perithecia borne in a loose mycelial felt; conidial 

 structures lacking or very limited in number; perithecia spherical or nearly 

 so, mostly 50 to 100m in diameter (fig. 42B), in fight tan shades, at first 

 consisting of parenchyma-like cells throughout but quickly developing fer- 

 tile tissue in central areas; asci evident within 4 to 5 days and ascospores 

 beginning to ripen within a week, fertile area progressing outward and 

 within 10 days to 2 weeks filling the entire peritheciuni except for a thin 

 peridium, one to two cells thick; asci borne as short branches from fertile 

 hyphae (fig. 42C), not in chains, spherical to oval or oblong, 8 to 10m in 

 diameter when mature, 8-spored; ascospores smooth, polished, broadly 

 elliptical to subglobose, 3.5 to 4.5m by 3.0 to 4.0m, comparatively heavy- 

 walled, without any indication of equatorial furrow or ridges (fig. 41D). 



Colonies on cornmeal agar spreading broadly, up to 6 cm. in 2 to 3 weeks, 

 very thin, vegetative mycelium submerged or forming a loose network at 

 the agar surface; perithecia rather sparsely produced — in form, dimensions, 

 and development as on malt agar; conidial stage lacking or very limited. 



Species description based upon NRRL 705 received without name by 

 Thom in 1936 from Dr. B. 0. Dodge as an isolate from modeling clay. 

 This culture has been maintained in our collection since that date as an 

 unidentified member of the general series with Penicillium brefeldianum. 

 Careful examination of this culture, during our cvu'rent study and detailed 

 comparison with described species leads us to regard the form as new. 

 The binomial, P. levitum, from the Latin levitas (smoothness), is applied 



