394 



VETERINARY BACTERIOLOGY 



however, it is probable that it occurs in all when grown under t he- 

 right conditions. 



The mycelium of Aspergillus is colorless and hyaline, 'much- 

 branched, penetrating for a short distance into the substratum or 

 medium, and usually sending up aerial hyphu>, which give the 

 colony a floccose or downy appearance. The hyphse are septate, 

 that is, cross walls are formed and the cells are divided from each 

 other by walls. Asexual reproduction takes place by the forma- 



Fig. 172. Morphology of the Aspergillus glaucus: a, Mycelia and perithecia 

 on the surface of the medium, with a single conidiophore; d, a very young peri- 

 thecium; e, cross-section through a perithecium, somewhat older; /, cross- 

 section through a mature perithecium, showing the asci and the ascospores 

 (as); 65 l , isolated asci; cc 1 , ascospores ripe and germinating (c b l d e f after 

 deBary, a b c l after Wehmer). 



tion of enlarged, erect, spore-bearing hyphae called conidiophores. 

 These conidiophores are inflated at the tip and become covered with 

 papillae, which develop into short stalks, called sterigmata (singular, 

 sterigma). The sterigmata may branch once or many times. 

 giving rise to bunches of secondary sterigmata, or they may remain 

 unbranched. The species wit h 1 > ranched sterigmata are frequent 1 y 

 grouped together into a genus Sterigmatocystis. From the tips of 

 these sterigmata spores or conidia are abjointed, .-md hanu together 

 to form long chains. The spore mass at the tip of the conidiophore 



