III. On a form ofBotrytis cinerea, with colourless sclerotia

Abstract

Botrytis cinereais perhaps the commonest and best known fungus, and has been a centre of mycological research since the time of de Bary. Few, if any other fungi, have been studied so thoroughly by so many able investigators, or are the subject of so extensive a literature; and one need only draw attention to the researches of de Bary (6), Pirotta (61), Marshall Ward (80), Kissling (45), Nordhausen (58), R. E. Smith (70), Farneti (27), Beauverie and Guilliermond (9, 10), Istvanffi (33), Reidemeister (65), and the more recent researches from the laboratory of Prof. V. H. Blackman (13, 16, 17, 84). There is a body of experimentally ascertained and exact knowledge concerning the bionomics of this fungus, which can be exceeded by that of few other micro-organisms. For the particular purposes in view in my investigations, it has been imperative that all experimental work be carried out with pedigree cultures. It was very early discovered that the ordinary "pure-culture" of mycological and bacteriological laboratories may be and very often is a poly-genotypic population, and that very considerable genotypic differences may usually be found in apparently homogeneous populations exhibiting only one single type, around which the individuals fluctuate. In order to eliminate this vitiating factor, single.-spore cultures were prepared either by Burri's (19) Indian-ink method, plate isolation, or, more usually, by a combination of the plate and dilution-drop method. These cultures served as the initial source of experimental material. In all, over seventy such pedigree stocks have been prepared from original sub-strata, representing about sixty different species of host plant, derived from all parts of the country. From these stocks some fifteen thousand cultures have been made. During the course of the investigation, many of these have been subjected to the most diverse environmental conditions, and all have been maintained under the closest scrutiny. With the exception of the single culture to be described, no change that could be interpreted as a permanent heritable alteration or mutation has been observed.