212 A MANUAL OF THE ASPERGILLI 



conidia globose about 6^ in diameter, with connectives. The description repeats 

 observations as to occurrence and appearance that are frequently seen. No one 

 has since reported a member of the A. candidus group with conidia 6m in diameter. 

 Whether the organism described by Saccardo was a large-spored mutant, not since 

 isolated, remains open to question. 



OTHER WHITE ASPERGILLI 



Other Aspergilli characterized by white heads but differing basically 

 in morphology from the A. candidus group occur in the Aspergillus glaucus, 

 A. nidulans, A. fumigatus, and A. terreus groups. Except for an absence 

 of spore color, these duplicate the morphology of the groups to which 

 assigned. In fact, in all cases except that of A. niveo-glaucus in the A. 

 glaucus group, they represent colorless mutations produced experimentally 

 from typical parent strains (Yuill, 1939; Steinberg and Thorn, 1940; Raper, 

 Coghill, and Hollaender, in press). While A. niveo-glaucus was isolated 

 from nature and hence its parentage is not known, it is suspected that 

 this represents a mutation of some form close to Aspergillus echinulatus. 

 A. halophilus of Sartory et al (Ann. Mycol. 28: (3/4) pp. 362-3, PI. 3, 1930) 

 similarly belongs in the A. glaucus group. Attention has been called earlier 

 to the fact that A. candidus differs from A. niger primarily in the absence 

 of color and in possessing smooth spores. The question may arise whether 

 we are not here dealing with a whole series of mutations from colored forms. 

 While this is possible, no proof is at hand. The fact that they constitute 

 such a typical and abundant element of the micropopulation of soil, decaying 

 vegetation, etc., demands that they be considered along with other major 

 groups of the Aspergilli quite aside from any questions of possible origin. 



Sclerotia 



In this arrangement of the Aspergilli, sclerotia, as compact globose or 

 subglobose bodies composed of thick-walled pseudo-parenchyma, are not 

 found in the groups characterized by the production of perithecia and 

 ascospores, and only rarely, if at all, in groups characterized by the presence 

 of hulle cells. In the great groups beginning with A. candidus, sclerotia 

 appear with sufficient frequency to be morphologically significant as 

 indicative of class relationship. Fundamentally, the typical A. candidus 

 strain differs little from the black Aspergilli except for the absence of the 

 dark color and rough spores. 



Group Relationships 



While there is much evidence of relationship with the black Aspergilli 

 (smooth-walled conidiophores, globose vesicles and heads, and the presence 

 of sclerotia), there are also certain indications of relationship to Asper- 

 gillus niveus. Typically both are characterized by snow-white conidial 



