CHAPTER XVII 

 THE HYPHOMYCETES ASPERGILLOSIS RINGWORM 



The Hyphomycetes 



THE moulds are, for convenience, collectively termed the Hypho- 

 mycetes, 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 multlccllular individuals, composed of filaments, simple 

 or branched, jointed or unjointed, which are termed hyphce, and are 

 formed by the end-to-end union of elongated cells. When the 

 hyphaa project upwards into the air they are known as aerial 

 hypha3, 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 hyphae 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 pro- 

 duce sexually formed spores by the fusion of two cells or gametes. 

 The two principal sexually formed spores are zygospores and asco- 

 spores. Zygospores occur in Mucor (see p. 470). In ascospore 

 formation, after conjugation of the gametes, instead of immediately 

 developing into a spore, the fertilised cell grows into a mass of branch- 

 ing hyphse, some of the cells of which produce spore sacs or asci, each 

 of which contains two or more ascospores (see Penicillium, p. 471). 



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

 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 

 sporangium as a sporangiophore. Some moulds produce spores by 

 segmentation of hyphee, these conidia being known as oidia t 



469 



