Mitosis in Vegetative Hyphæ of Higher Fungi (Hymenomycetes)

Abstract

TO find out mitotic stages, vegetative hyphæ of an agaric (wild variety of Psalliota campestris) and a polypore (Polyporus cuticularis), growing in culture on liquid 3 per cent malt medium, were fixed at intervals of half an hour from 2 p.m. to midnight; it was found by these trials that 8 to 8.15 p.m. (at night) was the most suitable period for demonstration of mitotic stages in these two cases under our laboratory conditions (temperatures of 25°–32° C.). A number of fixatives (such as Allen's Bouin, Carnoy, Navashin and Fleming's strong fluid) and stains (iron-hæmatoxylin, gentian violet, aceto-orcein and Feulgen) were used, of which the Fleming's strong fluid preceded by pretreatment in cold (15°–16° C.) for 1½ hr. with aesculin and 1 per cent saponin, and acet-orcein and Feulgen stains were found to be best. The squash technique of applying uniform pressure on the cover-slip readily brought out scattering and clarity of the small chromosomes which can scarcely be expected from the routine method of paraffin block-sectioning.