YEASTS AND MOULDS 335 



In this form lateral branches (gametophores) grow out 

 from two hyphae close to each other. These gametophores 

 meet by the tips, fuse, and then by septa the central 

 portion is separated off and becomes a " zygospore." 

 The mature zygospore under suitable conditions enlarges 

 and sends out a germ tube or hypha, on the end of which 

 a sporangium may appear. Mucor grows on gelatin plate 

 as round white colonies which soon cause liquefaction. In 

 gelatin stab, it forms a dense white growth spreading over 

 the surface, and sending down penetrating branches sub- 

 aerial hyphae ; others rise up vertically into the tube- 

 aerial hyphae. Other mucors are : M. stolonifer (black 

 mucor), M. spinosus (chocolate colour : has spines on the 

 columella) . 



Aspergillus or "Knob" Mould. This is a common 

 form of mould, occurring on bread, cheese, oranges, etc. 

 There are several varieties, A. glaucus (blue mould), A. 

 niger (black mould), A. flavus (yellow mould), and A. 

 fumigatus (green turning to grey). The mycelial filaments 

 are composed of numerous rod-like cells joined end to end. 

 They reproduce asexually. Hyphae arise from the mycelial 

 network, and each hypha terminates in a knob-like expan- 

 sion, the columella. The surface of the columella becomes 

 studded with flask-shaped organs or cells called sterig- 

 mata, and each of these forms spores or conidia, which 

 remain attached in chains like streptococci. The result is 

 a knob with radial projections composed of spores ; but 

 having, unlike Mucor, no containing capsule. 



Aspergilli grow on gelatin as round white colonies very 

 like those of penicillium. In a few days coloured points 

 appear, denoting spore formation, being blue in glaucus, 

 black in niger, etc. The gelatin is liquefied. In gelatin 

 stab there is a dense felt-like growth (more pronounced 

 than with penicillium), and later liquefaction. 



The pathogenic aspergilli include : 



i. Aspergillus fumigatus, which has been found on the 

 one hand in a malady simulating pulmonary tuberculosis, 

 but not showing tubercle baciUi in the sputum (at times 

 it is associated with the tubercle bacillus) ; and on the 

 other hand, causing affections in the external auditory 

 canal, the tympanic cavity, the nasal fossae, and in wounds. 



