MORPHOLOGY AND DESCRIPTION 27 



and are never more than loosely hung in networks of hyphae; they are 

 often very abundant and dominate the color of the colony. Perithecium 

 formation is favored by abundance of assimilable carbohydrate, but may 

 or may not be completely suppressed by its replacement with nitrogenous 

 products ; transfers from the same culture have developed colonies yellow 

 from perithecia when grown on sugar solution, or dense green without 

 sign of perithecia upon a peptone medium or a piece of leather. 



The perithecium of Aspergillus arises from a branch which coils in various 

 manners in the different species to become the ascogone, as figured by 

 Dangeard from forms reported as E. herbariorum, A. flavus, A. fumigatus, 

 S. ochracea, S. nidulans, by Fraser and Chambers for A. herbariorum, and 

 by Dale (1909) for A. repens. No fertilization process was demonstrated 

 in those studies. Dangeard (1907) reported the cells in the fruiting 

 apparatus as multinucleate in E. herbariorum, but to be mononucleate 

 in the other species figured. In general, however, the development of an 

 ascogone, followed by the development of the perithecial wall and accessory 

 cell masses from vegetative hyphae below the ascogone, has been roughly 

 described and figured for the group represented by A . glaucus and A . nidulans 

 but interpretation of the other specific names used by Dangeard is doubtful, 

 even for grouping, on the basis of the descriptions and figures given. 



Henrard (1934), working with 15 "species" of Aspergilli, reports that 

 all of them are "sexually homothallic." He summarized the literature 

 by saying that homothallism in the Aspergilli has been affirmed by Kniep 

 (1928) for A. repens; by Schwartz (1928) for A. ruber, A. repens, four 

 other strains of "A. glaucus", and four strains of A. nidulans; by Blochwitz 

 (1932) for six strains in the A. glaucus group; and by Greene (1933) for 

 A. fischeri. 



So far then, as present information goes, heterothallism cannot be assumed 

 to account for the great variability of the Aspergilli. 



Perithecia are regularly found in most of the species of the A. glaucus 

 group and in A. fischeri, which is closely related to A. fumigatus, and in a 

 series of closely related forms in the A. nidulans group. They are not 

 sporadic or dependent upon unknown conditions, but are regularly pro- 

 duced in media which are adequately supplied with sugars and the salts 

 in routine use. Their presence in A. wentii and A. citrisporus was asserted 

 by Thaxter (personal communication) without producing either material, 

 or description of the ascospores. Dangeard (1907) claimed to have found 

 ascospores within the sclerotia of A. niger but failed to describe them. 

 Diligent search over many years has failed thus far to confirm either 

 statement. Still, it may be assumed that such sclerotia may be the 

 homologue of structures which under some conditions might become peri- 

 thecia. 



