Societies and Academies

Abstract

LONDON. British Mycological Society, November 20.—W. J. Dowson: An unusual species of Botrytis attacking Narcissus. The fungus is the cause of ‘fire,’ marking the leaves with one or more yellow patches. The spores of the fungus are very large, and germinate with as many as thirteen germ tubes after up to one hour in water or in dilute glycerine.—Miss A. Lorrain Smith: A new family of lichens. The lichen Cryptothecia subnidulans was described by the late Dr. Stirton, and has led to much difficulty in assigning it to a systematic position. Stirton's herbarium has revealed three additional species of the genus and two closely allied ones for which a new genus is proposed; the two genera form a family characterised by the apparently double walled ascus containing septate or muriform spores and embedded in a lax peridium of interwoven hyphae. Affinity with the fungi Myriangiales and Gymnoascales is suggested; the nearest lichen allies appear to be Thelocarpaceaa and Mycoporacea.—O. V. Darbishire: Isidia and soralia of lichens. Isidia in Peltigera prætextata develop endogenously from special hyphme which make their way to the surface, breaking through the cortex or making use of a crack. The mature isidia are very highly developed assimilators. There is a primary cortex on the upper surface with walls of wavy outline. The secondary cortex is similar to the cortex of the thallus. The gonidia are fairly closely packed towards the upper cortex with a very loose arrangement just inside the lower cortex. This cortex is of one layer of cells, with sinuate walls and interrupted here and there by pores. Soredia also have an endogenous origin. A few gonidia are gradually surrounded by the fungus and the differentiating soredium is raised to the surface of the sorial tissue, from which it becomes detached as a reproductive organ.—W. R. I. Cook: The genus Ligniera. Cross inoculations have shown that several species which have been described are merely host varieties. Infection takes place by zoospores entering root hairs. Spores serve as a resting stage and for propagation within the plant. Reduction division occurs at the formation both of spores and zoospores. Conjugation has not been seen.-W. A. Roach: On the nature of disease resistance in plants, with special reference to the wart disease of potatoes. Wart disease is an example of physiological resistance. Evidence at present suggests that immune and susceptible varieties form two distinct classes and not end members of a continuous series. The reaction towards wart disease is unaffected by grafting on either a foliage system, a root system, or of a complete plant of opposite reaction to the disease. Immunity from, or susceptibility to, wart disease is therefore probably innate to the cell and must be sought in compounds which cannot cross a graft fusion layer unchanged, and so probably cannot leave a cell. These compounds may be proteins.