Abstract
Edinburgh. Royal Society, June 15.—A. H. Reginald Buller: (An address) Recent advances in our knowledge of the higher fungi. A mushroom is the reproductive part of the mushroom plant and is produced at the expense of the mycelium or spawn. A large mushroom may develop and liberate upwards of 10,000,000,000 spores. The basidiospores of all Hymenomycetes, all Uredineæ, the smut-genus Tilletia, and the yeast-genus Sporobolomyces are shot away by a drop-excretion mechanism, but exactly how this mechanism works is still a profound mystery. The terminal rate of fall of spores in still air varies with the size of the spores from about 0.5 to 4.0 mm. per sec. Spores are discharged from the under side of the caps of mushrooms and toadstools in a continuous stream for days or weeks. The clouds of spores escaping from a fruit-body can be made visible in a darkened room by means of a beam of light. Nocturnal excursions with an electric lamp may be made to observe spore-discharge from fruit-bodies attached to tree-trunks, etc. The organisation of the hymenium which covers the gills of mushrooms and toadstools has been worked out, and the time and space relations of the basidia which produce the spores and of the sterile elements called paraphyses are now known. The basidia come to maturity in a series of successive generations. The sexual process in mushrooms and toadstools is initiated in the mycelium with nuclear association, is continued there with conjugate nuclear divisions, and is completed in the fruit-body by nuclear fusion in every basidium.—J. Thomson: The ionising efficiency of electronic impacts in air: Experiments are described, the aim of which is the determination of the average energy required to produce one pair of ions in air by electronic impact, the initial energy of the electron being defined. The results show that the total number of ions produced is a linear function of the initial electronic energy. Hence it is shown by extrapolation that for fast-moving electrons (such as β-rays) the energy per ion-pair is 37 ± 2 electron-volts. This result is discussed in relation to other investigations, and the extrapolation is thereby justified.
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Societies and Academies. Nature 128, 81–83 (1931). https://doi.org/10.1038/128081a0
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DOI: https://doi.org/10.1038/128081a0