272 BACTERIOLOGY FOR NURSES 



hyphae are segmented by transverse walls, each filament consist- 

 ing of cells placed end to end. 



Among the phycomycetes, of which Mucor mucedo, the white 

 cottony mold which grows in damp bread, is a familiar example, 

 reproduction may take place asexually or sexually; the former 

 method is the most usual. The end of a hypha becomes shut off 

 by a transverse wall and the extremity then swells into a globular 

 sac or sporangium within which numerous oval spores develop. 

 The swelling of the gelatinous mass in which the spores are em- 

 bedded ruptures the thin cell wall and the spores thus escape. 



Other forms of asexual repro- 

 duction occur amongst these 

 lower forms, one of which is 

 the production of thick-walled 

 spores termed chlamydospores, 

 which possess a much higher 

 degree of resistance than the 

 thin-walled variety. Under cer- 

 tain conditions the conjugation 

 of two cells precedes spore for- 

 mation (sexual reproduction). 

 So-called gametophores occur 



FIG. 40. Mucor Mucedo. ,1 -U-L 



as outgrowths m neighboring 



hyphse, and when the tips of the two gametophores come in con- 

 tact they fuse, transverse septa are formed, and a zygospore is 

 the result. From the matured zygospore a germ tube arises which 

 may begin to function at once in the usual manner (Fig. 40). 



The mycomycetes reproduce almost invariably by asexual spore 

 formation. Two main groups are recognized on the basis of their 

 method of forming spores. In one series a cell or ascus is formed 

 at the end of a hypha and within it is produced a number of spores 

 constant to the species. The number is always a multiple of two, 

 usually eight. The group having asci is known as ascomycetes. 

 In the second series no spore sac is formed. The terminal portion 

 of a hypha segments into germinating branches known as conidio- 

 phores. These conidiophores divide into two or three branches, 



