THE ASPERGILLUS VERSICOLOR GROUP 189 



54 I) and occasionally conspicuously elongate, typically fertile over the 

 entire area, ranging in size from 20 to 30/x by 12 to 18/z. Sterigmata in 

 two series, rather loosely arranged, primaries 7 to 10m by 4 to 4.5m; sec- 

 ondaries 6 to 8.5^ by 2 to 2.8m- Conidia dark green in mass, conspicuously 

 spinulose (fig. 54 I), globose, mostly 2.5 to 3.5/x, occasionally larger or 

 smaller. 



Conidial heads of mixed character, containing both white and green 

 spores, commonly encountered (fig. 54 E), usually borne upon long conidio- 

 phores approaching and often equalling in length those of white heads, 

 vesicles clavate (fig. 54 H), sterigmata at first bearing colorless smooth- 

 walled conidia, but subsequently bearing dark green spinulose conidia. At 

 temperatures of 24° C. and above, thick-walled hulle cells abundant, irregu- 

 lar in form (fig. 54 F), commonly globose to subglobose, not infrequently 

 elongate, commonly more or less curved and often lobed. 



Colonies upon malt extract agar growing luxuriantly (fig. 54 B), generally 

 loose in texture with aerial mycelium prominent, conidial heads normally 

 more abundant than upon Czapek agar, the proportion of white to green 

 heads varying with the temperature of incubation. 



Colonies upon hay infusion agar spreading broadly, consisting of a thin 

 submerged mycelium from which develop erect, white and green conidial 

 structures, the relative proportion of these types being dependent upon the 

 temperature of incubation ; since comparatively meager growth occurs upon 

 this medium, and since there is a minimum of aerial vegetative hyphae, it 

 constitutes a very favorable substratum upon which to observe the forma- 

 tion of the contrasting fruiting structures characteristic of the species. 



The binomial Aspergillus janus was selected for this species because of the 

 contrasting types of conidial heads produced — it is literally a "two-faced" 

 mold. 



Type culture NRRL No. 1787 was isolated in February 1942 from 

 Panama soil collected during the summer of 1941 by John T. Bonner of 

 Harvard University. Three additional isolations by members of the 

 Northern Regional Research Laboratory staff have since been made from 

 Panama soils subsequently collected by Mr. Benjamin T. Coghill. 



It is believed that this species represents a normal component of the 

 microflora of Panama. Additional evidence in support of this view is 

 furnished by the fact that in 1925 Professor Roland Thaxter sent to Thorn 

 under the label "white Panama Aspergillus" a representative of this species. 

 The form was never described by Thaxter, and viable cultures of it were lost 

 from our collection some time prior to 1930. As the correspondence of the 

 time is remembered, Thaxter was plagued by the presence of a small green 

 mold which repeatedly appeared in his cultures as a "contaminant." 

 Fortunately, the original tube received from Thaxter has been preserved, 



