Some Experiments on the Effect of External Stimuli on the Sporidia of Puccinia malvacearum (Mont.)
Abstract
Downloaded from aob.oxfordjournals.org at Infovell on November 13, 2010 Platt Botanical Scholar in tht University of Manchesttr. With seven Figures in the Text. N certain preliminary experiments in which the sporidia of Puccinia malvacearum were germinated near a fragment of hollyhock leaf, it was observed that all the germ tubes grew in one direction, and pointed towards the leaf fragment. This at first suggested positive chemotropism. More critical work, however, revealed the fact that it was an effect produced by the unilateral illumination of the sporidia. This led to the investigation of the tropic influences affecting the germinating sporidia of Puccinia malvacearum. De Bary 1 first raised the question as to why the germ tubes of parasitic fungi turn towards, and penetrate the tissues of their host-plants. Even before the publication of the work of Pfeffer on external de Bary suggested that ' physical irritations' or chemical might play a part in these phenomena. Later, as a result of numerous experiments on the chemotropism of Fungi, Miyoshia concluded that certain chemical substances attract the germ tubes of Fungi, whilst .others repel them. Nordhausen 8 accepted Miyoshi's results and investigated the biology of the penetration of plant tissues by