Nuclear Migration in Gelasinospora

Abstract

SUMMARY In Gelasinospora tetrasperma, one of the Pyrenomycetes, the migration of nuclei from a mycelium of one sex into a mycelium of opposite sex has been confirmed. Migrating nuclei have been found to travel through a mycelium at a speed of from 4 mm. to 5 mm. per hour. It was shown that two mycelia of opposite sex, on coming into contact on an agar plate, fuse with one another but do not overgrow one another and that the speed of nuclear migration may be twice or three times the rate at which living hyphae grow in length. Light influences the migration of nuclei. In mating experiments it was found that nuclei move from a darkened mycelium of one sex toward and into an illuminated part of a mycelium of opposite sex. Migrating nuclei move from cell to cell via the minute central pore in the transverse septum. In Gelasinospora tetrasperma, as in other Pyrenomycetes, columns of cytoplasm are constantly flowing toward the tips of the growing hyphae. When cytoplasm is being evacuated from older cells in a mycelium and is passing toward the growing hyphal tips, the nuclei of the older cells are not carried away in the stream of cytoplasm but remain anchored to the thin fixed layer of cytoplasm that is pressed against the cell-wall and that forms the bounding layer of the vacuoles. The mechanism which enables nuclei to migrate from a mycelium of one sex into and along a mycelium of opposite sex is at present unknown.