Ill] 



PLECTASCALES 



69 



liberated by its decay. The asci are spherical or pyriform and contain two 

 to eight continuous spores, the walls of which may be variously ornamented. 

 In both Penicillium and Eurotium the perithecium may develop an excep- 

 tionally thick wall, and pass into a resting stage sometimes several weeks 

 in duration. Such a structure is described as a sclerotium. 



In Eurotium herbariorum 1 the development of perithecia is readily 

 induced by cultivation on prune agar 2 made up with forty per cent, of cane- 

 sugar. Ripe perithecia appear after ten days or a fortnight at 15 C. 

 A similar method should probably prove successful with other species. 



The only known species of Aphanoascus, A. cinnabarinus, was found by 

 Zukal on the dung of alligators. The character of its perithecium wall 

 (fig. 28) suggests a transition stage between the Gymnoascaccae, in which it is 



Fig. 18. Aphanoascus cinnabarinus Zukal ; a. elongated, septate archicarp and swollen 

 antheridium ; b. ascogenous hyphae and sheath; after Dangeard. 



placed by Dangeard, and the Aspergillaceae. Multinucleate conidia are borne 

 laterally or terminally on the mycelium. The sexual organs arise from the 

 same or different hyphae; the antheridium (Dangeard's trophogone) becomes 

 swollen, and the elongated archicarp, which appears at first to be without 

 septa, coils round it; their fusion has not been observed. Each at first 

 contains from three to ten nuclei; later the number rises to about twenty 

 in the antheridium and as many as forty in the archicarp. According to 

 Dangeard the contents of the antheridium degenerate, though the cell itself 

 persists for a considerable time. The archicarp undergoes septation, branches, 

 and gives rise to asci. In the meantime vegetative hyphae grow up and 

 invest the essential organs, forming a loose tangle around them The inner 

 part of the investment remains in this state and is eventually absorbed, but 



1 Eurotium herbariorum (Wigg.) Link = ^~. Aspergillus glaucits de Bary, and Aspergillus 

 herbariorum Wigg. 



- Ten prunes are placed in a small saucepan of water and allowed to simmer, being broken open 

 when soft; when the fluid is reduced to about looc.c. it is poured off, the sugar dissolved in it and 

 five per cent, agar agar stirred in. Material grown on this medium is excellent for class work ; it 

 should be examined under the microscope while still attached to a thin slice of agar. 



