178 A MANUAL OF THE ASPERGILLI 



both comparatively short and stout; primaries 3.5 to 5.0m by 3.0 to 4.0m; 

 secondaries 4.0 to 5.5m by 3.0 to 3.5/z, commonly bottle-form. Conidia 

 globose, pale green, delicately echinulate. Mostly 4.8 to 5.5/x in diameter, 

 rarely larger. Hiille cells abundant, irregularly globose, ovoid or somewhat 

 elongate, commonly 12 to 30m in long axis, walls heavy, 4 to 5m in thickness, 

 borne primarily in small, colorless clusters which are quite conspicuous at 

 colony margins and lend to them a characteristic granular appearance. 



Colonies upon malt extract agar showing an accentuation of hiille cell 

 development (fig. 50 B) and a reduction in conidial heads. Otherwise 

 duplicating the cultural picture presented upon Czapek's solution agar. 



Colonies upon hay infusion agar (fig. 50 A) thin but broadly spreading, 

 characterized by scattered clusters of hiille cells and erect conidial fructifica- 

 tions giving to the culture a sparsely granular appearance. 



Type culture NRRL No. 1932 was isolated in 1942 from a sample of soil 

 collected in Fayetteville, Arkansas, and contributed by Mr. F. R. Earle. 

 Additional strains have been isolated from soils collected in Texas, Arizona, 

 and Costa Rica. It is believed common in soils where the temperature 

 remains at a high level during part or all of the year. 



Different strains vary materially in the number of conidial heads pro- 

 duced upon common laboratory media such as Czapek's solution and malt 

 extract agars, ranging from abundant heads in some to only widely scattered 

 heads in others. All fruit reasonably well, however, upon hay infusion agar, 

 the medium upon which original isolations were made. 



The brown color of the conidiophores, the presence of ovoid to somewhat 

 irregular hiille cells, and the green color of its conidia place this species in 

 the group with A. ustus. It differs markedly from the more common 

 representatives of this group, however, in the lighter and persistently green 

 color of its conidia, the small clusters rather than irregular masses of hiille 

 cells, and in possessing somewhat more elongate vesicles. In this latter 

 character it suggests Aspergillus flavipes but is in turn excluded from this 

 group by the green color of its spores. 



Occurrence and Economic Importance 



Representatives of the Aspergillus ustus group are perhaps the most 

 abundant of all aspergilli in soil. They regularly occur in large numbers 

 and in considerable variety. The common species, A. ustus, occurs alike 

 in cultivated and forest soils and in approximately equal abundance in 

 soils from southern and from north temperate areas. A. granulosus, on 

 the contrary, has been isolated only from southern sources. Members of 

 the group are not known to be particularly active agents of decomposition, 

 but their great abundance in nature is believed indicative of a significant 

 role in many decay processes. 



Their biochemical activities and potentialities are almost completely 

 unknown. 



