Basidiospores of Several Species of Agaricales Discharged and Collected in Pairs

Abstract

While collecting spore prints of Agaricus bisporus (Lange) Sing. for single-spore isolations, we noticed that the spores appeared in pairs on the collecting surface. Since this phenomenon was unexpected in the light of Buller's classical studies, a series of tests were undertaken to learn whether pairing occurred regularly or only under very special conditions. Most of these tests were made in small settling towers in which sporophores were suspended about 15 centimeters above the collecting surface. The sporophores were harvested when mature and secured in position in the towers with their gills or pores as nearly vertical as possible. The spore prints were collected on glass microscope slides and usually observed without cover slips under low power of a compound microscope. We soon learned that the identity of pairs of spores is obscured by crowding and overlapping when the spore prints are too dense. Pairs are clearly apparent, however, when only 20 to 40 spores are distributed on the glass slides within a low-power microscope field. In some instances a suitable spore density was obtained in 10 seconds, but in other cases as long as 5 minutes was required. Whenever spore discharge was normal and abundant, several pairs of spores could be seen in each square millimeter of the collecting surface (FIGS. 1-4). In one series of tests sporophores were suspended at different heights above the glass slides. In these tests paired spores were clearly evident on the slides even after the spores had settled through a vertical distance of 1 meter. We interpreted this as evidence that each pair came from the same basidium and made the journey together to the collection surface. The paired spores must be discharged from the basidium simultaneously or at most within -i second of each other. Otherwise, how can they fall in slightly turbulent air