This conjugate condition is finally brought to a close by the nuclear fusion in the basidium.
It is probable that in all cases nuclear fusion takes place sooner or later.
We know very little of the details of reduction in the lower plants, but it probably occurs at some stage in the life history of all plants in which sexual nuclear fusion takes place.
Between the nuclear association and the nuclear fusion in the basidium many thousands of cell generations may be intercalated.
The theory may be put forward that the ordinary forms have been derived from sexual forms like Schizosaccharomyces and Zygosaccharomyces by a loss of sexuality, the sporangium being formed parthenogenetically without any nuclear fusion.