CHLAMYDOSPORES 5 



These free cells may be formed by a segmentation of the mycelium 

 into its component cells by a split through the septa. The resulting 

 cells may be cylindrical in form (Fig. 119) as in Geotrichiim 

 candidum, or may become rounded as in Mucor racemosus (Fig. 36). 

 Free cells formed in this way are known as oidia. They may give 

 rise to new free cells by division or by budding, or may give rise to 

 mycelium. Free cells may also arise from the mycelium by either 

 lateral or terminal budding, as also occurs with M. racemosus (Fig. 

 37) and with the various species of Candida (Fig. 116). These may 

 also form either new free cells (by budding) or mycelium, depending 

 upon their environment. 



Such free cells differ from spores in that they are not equipped 

 for maintaining life in a dormant condition for long periods of time. 

 They do serve, however, to multiply rapidly and disseminate the 

 species, especially in liquid media. They are to be looked upon as 

 "growth forms" rather then specialized reproductive bodies. The 

 conditions which determine their appearance are quite diverse for 

 different species. Thus in Mucors they are formed only under semi- 

 anaerobic conditions, whereas in Candida they are predominant in 

 aerobic cultures in sugar media. 



These oidia or free cells bear a great resemblance to and may be 

 readily mistaken for true yeasts, especially when they multiply by 

 budding. In fact, as will be shown later, yeasts are probably de- 

 scended from more complexly organized fungi, which have perma- 

 nently lost the power to produce mycelium and maintain only the 

 one-celled growth form. But, as pointed out above, yeast-like cells 

 may be formed under certain circumstances by representatives of all 

 the great classes of fungi, Phycomycetes, Ascomycetes, and Basidio- 

 mycetes. Similarly we may trace, with the true yeasts, evidences 

 (in their spores) of relationships to at least two of these classes, 

 Ascomycetes and Basidiomycetes. Yeasts, then, are a heterogeneous 

 group of fungi which maintain a unicellular growth form, and are 

 not an independent class of organisms. Their classification together 

 is only for convenience and does not imply a true systematic rela- 

 tionship. 



Chlamydospores. With many species of fungi we may find a cell 

 here and there in the mycelium (including the submersed or vegeta- 

 tive portion) which becomes differentiated from the others by in- 

 creased size, due to the storage of much reserve foodstuff, and by a 

 markedly thickened cell wall. These are known as chlamydospores. 

 They are particularly adapted for maintaining vitality through long 



