CHAPTER IX 

 ENDOMYCETALES 



The Endomycetales include those forms in which an ascus arises directly 

 as the product of a sexual act, wherever this occurs. They comprise eleven 

 families distributed among four diverging lines of degeneration. In the most 

 primitive family, the Spermophthoraceae, the mycelium is nonseptate and 

 coenocytic, the gametes are differentiated and freed from the gametangium, 

 and a septate uninucleate secondary mycelium results. From this primitive 

 family we have four diverging lines of degeneration, each line having a char- 

 acteristic spore shape. In the Ashbyaceae, the mycelium, when present, may 

 be septate, but the cells are usually coenocytic and have the elongate fusiform 

 ascospore of the Spermophthoraceae (Fig. 13, 1-3). In the Ascoideaceae — 

 Endomycetaceae line, the mycelium becomes uninucleate, the ascospores, 

 which in the early stages of its development are fusiform, become cucullate 

 (Fig. 13, 10), or the rim assumes an equatorial position, producing a saturnine 

 spore (Fig. 13, 6). The position of the Pichiaceae is not clear. Here the 

 ascospores are hemispheric or slightly angular (Fig. 13, 7, 8). They may pos- 

 sibly be derived from GuiUermondeUa (Fig. 13, 5), a member of the Ashbyaceae, 

 or more probably Hanseniospora, one of the Endomycetaceae with rough cucul- 

 late spores, by the loss of the rim (Fig. 13). 



In the two remaining lines, the spores are ellipsoid or spherical and have 

 probably diverged from the Spermophthoraceae through Dipodascus. One line 

 retained strong evidence of sexuality, gradually losing it with extreme degenera- 

 tion, producing its spores saprophj'tically, and early reducing the ascospore 

 number to 8, 4, or fewer. This line is represented by the Eremascaceae and 

 Saccharomycetaceae. The other line promptly discarded traces of sexuality, 

 produced its spores in the host tissue, very rarely under saprophytic condi- 

 tions, and retained the large number of ascospores of the Dipodascaceae. This 

 latter line is represented by three strictly parasitic families, one comprising 

 predominantly mammalian parasites, the other two plant pathogens. There is 

 a small residue of species usually placed in the Saccharomycetaceae, in which 

 the ascospores copulate in pairs. Their systematic jDosition is not clear. Guil- 

 liermond has recently (1931) suggested that this group of species has been 

 derived from the Taphrinaceae, the end member of the fourth line mentioned 

 above. 



Key to Families 



Gametes fusiform, set free from the gametangium, copulating in pairs, producing an 

 ascogenous hypha; ascospores fusiform. Spermophthoraceae. 



Gametes not set free, gametangial copulation the usual type, or the ascospores develop 

 parthenogenetically. 

 Ascospores fusiform to acicular. Ashbyaceae. 



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