Chapter XVI 

 THE ASPERGILLUS CANDIDUS GROUP 



Outstanding Characters 



Conidial heads persistently white or becoming yellowish cream in age; 



typically globose, but approaching columnar in small heads. 

 Conidiophores smooth, colorless or slightly yellowed in terminal areas. 

 Sterigmata in two series, with primaries often much enlarged, sometimes 



varying greatly in size within the same head. 

 Conidia globose or subglobose, smooth. 

 Sclerotia present in some strains, dark, approaching purple to black 



when mature. 



Grouping by color lead Thorn and Church (1926) to establish their Section 

 IX, or the so-called "White-spored Aspergilli." Only vaguely did they 

 indicate that they had included a heterogeneous lot rather than described 

 a natural group. Further study of the strains included in the "white" 

 section showed the tardy development of colors approaching avellaneous 

 or even carneus. The continued comparison of great numbers of strains 

 in all groups has revealed such wide variations in color that the authors 

 have come to regard whiteness, or lack of color, as a character of secondary 

 importance in the allocation of strains to particular groups. This view- 

 point is supported by the appearance, under controlled conditions, of 

 white variants or mutants in a number of colored series. Yuill (1939) 

 observed and isolated such colorless mutants from Aspergillus fumigatus 

 and A. nidulans; Steinberg and Thom (1940) reported the same type of 

 mutant for the former species; while Raper, Coghill, and Hollaender (in 

 press) have succeeded in producing white mutants in Aspergillus terreus 

 by irradiating spores with ultra-violet. Colorless members of the Asper- 

 gillus glaucus group, represented by A. niveo-glaucus, have been isolated by 

 Blochwitz, Thom and Raper, and other investigators. Long before the 

 work of Yuill, Schiemann (1916) had developed two color variants of 

 Aspergillus niger, A. schiemanni (Schiemann) Thom (1926, p. 172) 

 and A. cinnamomeus Schiemann (1912) which differed only from the 

 parent strain by a progressive reduction of the amount of coloring 

 substance, presumably the aspergilline of Linossier (1891). Steinberg 

 and Thom (1940), working with a strain of A. niger, again produced 

 variants approximating those of Schiemann, and Whelden (1940) secured 

 the same by irradiating spores of A. niger with cathode rays. In cultures 



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