CHAPTER XVII 



THE HYPHOMYCETES ASPERGILLOSIS RINGWORM 



The Hyphomycetes 



THE moulds are, for convenience, collectively termed the 

 Hyphomycetes, but this is not a strict botanical group. They are 

 Fungi having as a common character a plant body made up of 

 hyphse. They are multicellular individuals, composed of fila- 

 ments, simple or branched, jointed or unjointed, which are 

 termed hyphce, and are formed by the end-to-end union of elon- 

 gated cells. Whon the hyphse project upwards into the air they 

 are known as aerial hyphse, and when downwards into the fluid 

 or medium on which the organism is growing as submerged hyphse, 

 and the compact tufts or masses resulting from interlacing hyphse 

 are termed mycelia. A mycelium may form a hard lignified mass 

 or pseudo -parenchyma, which is known as a sclerotium, such as is 

 met with in ergot and in the black variety of mycetoma. 



Any piece of the mycelium will grow, but in addition moulds 

 reproduce by multiple spores, which may be asexual or sexual. 

 Practically all moulds produce asexually formed spores ; some 

 produce sexually formed spores by the fusion of two cells or 

 gametes. The two principal sexually formed spores are zygospores 

 and ascospores. Zygospores occur in Mucor (see p. 569). In 

 ascospore formation, after conjugation of the gametes, instead of 

 immediately developing into a spore, the fertilised cell grows 

 into a mass of branching hyphse, some of the cells of which produce 

 spore sacs or asci, each of which contains two or more ascospores 

 (see Penicillium, p. 570). 



Asexual spores are either free, borne at the ends or sides of 

 hyphse conidia as in Penicillium, or are formed in specialised 

 spore cases sporangia as in Mucor. 



Usually the spore-bearing hyphse are specially differentiated, 

 and one bearing conidia is known as a conidiophore, one bearing a 



