Chapter XII 

 THE ASPERGILLUS USTUS GROUP 



Outstanding Characters 



Colonies more or less floccose, at first white but becoming dull in age, in 

 most members varying from olive-gray through reddish-brown to 

 fuscous, as conidial structures develop. 



Conidiophores in yellow-brown shades; smooth. 



Heads irregular in form, ranging from more or less radiate to hemi- 

 spherical to loosely columnar. 



Vesicles hemispherical; sterigmata in two series, loosely arranged. 



Conidia roughened, 3.0 to 5.0m, varying from echinulate to marked with 

 conspicuous color bars, and ranging in color from pale blue-green 

 through olive-green shades to deep brown (fuligineus). 



Hulle cells regularly present, thick-walled, elongate, often more or less 

 curved and twisted. 



Included here are representatives of a most abundant and widespread 

 group of fungi, especially common in soil and upon decaying vegetation. 



Group Key 



Colonies predominantly floccose, heavy sporing, hiille cells not aggregated in small 



clusters A. ustus (Bain.) Thorn and Church 



Colonies more or less floccose, light sporing, hiille cells aggregated in small clusters 



A. granulosus Raper and Thorn 



Aspergillus ustus (Bainier) Thorn and Church, in The 

 Aspergilli, p. 152. 1926. 



Synonym : Sterigmatocystis usta Bainier, in Bui. Soc. Bot. France 28 : 

 78. 1881. 



Colonies upon Czapek's solution agar spreading broadly, plane, sulcate, 

 or umbonate, rarely zonate, more or less felted or floccose; at first white, 

 becoming olive-gray, yellow-brown, fuscous or russet to purplish vinaceous 

 with the development of mature conidial structures (PI. IV E, and figs. 

 48 A and B) ; generally heavy sporing, with some conidiophores arising from 

 the substratum but more abundantly from aerial hyphae ; reverse in shades 

 of yellow, orange, and brown to almost black in age; odor not pronounced. 

 Heads radiate to irregularly hemispherical, sometimes loosely columnar, 

 commonly splitting into more or less well-defined columns in age, very 

 variable in size, ranging in color from dull green or olive-gray, through gray- 



171 



