. Comparative morphology of Fungi. Fungi. IIEMIASCOM YCETES 155 tendency often attract a third of different tendency. Occasionally copulation may be retarded and the tubes attain a considerable length or, as the ascus is torn by them, they may grow into the open. Further- more, the copulation processes may go in a meridianal direction and fuse with the spores of the other pole; or the spores may develop unsimultane- ously or abort, in which case fusion with spores of another ascus may occur (Fig. 97, 9). Finally, as an exception, the spores may germinate parthe- nogenetically, especially in ol
. Comparative morphology of Fungi. Fungi. IIEMIASCOM YCETES 155 tendency often attract a third of different tendency. Occasionally copulation may be retarded and the tubes attain a considerable length or, as the ascus is torn by them, they may grow into the open. Further- more, the copulation processes may go in a meridianal direction and fuse with the spores of the other pole; or the spores may develop unsimultane- ously or abort, in which case fusion with spores of another ascus may occur (Fig. 97, 9). Finally, as an exception, the spores may germinate parthe- nogenetically, especially in old cultures, in which case there results a special strain which only germinates parthenogenetically; it does not differ morphologically from the original strain, and forms a germ tube which ruptures the ascus wall. After the copulation processes have come into open communication, the nuclei migrate into the bridge and fuse (Fig. 97, 6 and 7); occasionally the fusion may occur in one of the spores instead of in the canal or may. Fig. 97.—Saccharomyces Ludwigii. Copulation and development of asci. (X 750; after Guillcrmond, 1905.) be retarded and take place only in the germ tube which grows out of the copulation canal, breaks through the ascus wall and germinates to a sprout mycelium. If one imagines this copulation entirely suppressed (as occurs in cer- tain strains), one arrives, as in the Torulaspora-Schwanniomyces series, to asexual forms of Saccharomyces cerevisiae. Only these forms, in contrast to the former, would be regarded as apogamous since their thallus belongs to the diplonts. The forms of the S. cerevisiae type thus may be considered biphyletic, where it is not easy to distinguish which belong to the partheno- genetic and which to the apogamous groups. It need hardly be said that in reality the roots of these asexual forms are much more numerous and that the Saccharomycetaceae form a polyphyletic family since Endo- myces capsularis and its relatives could have led
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