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Societies and Academies

Nature volume 100, pages 319320 (20 December 1917) | Download Citation



LONDON. Linnean Society, November 29.—Sir David Prain, president, in the chair.-Dr. H. Wager; (1) Intensity and direction of light as factors in phototropism. In this communication an account is given of experiments made to determine the influence of the intensity and the direction of light in effecting phototropic responses in foliage leaves. The distribution of the physico-chemical activities in the photo-sensitive tissues is dependent upon both intensity and direction of light, and since the direction of movement may be determined as the resultant of the varying physico-chemical activities in the whole of the sensitive region, it must be concluded that both intensity and direction of light are necessary factors in the photo-tropic response. (2) Spore-coloration in the Agari-cacese. The use of spore-coloration as a basis for the classification of the Agaricaceae is artificial and imperfect. There is no clear line of demarcation between the various colours, and the designation of the colours in the text-books is very indefinite and unsatisfactory. A beginning has, however, been made by members of the Mycological Committee of the Yorkshire Naturalists' Union to obtain more accurate records of spore-coloration in terms of a standard series of tints. It has been found and this may be a fact of some considerable physiological interest-that, with one or two doubtful exceptions, all the spore colours so far standardised, whether pink, rusty, or purple, fall within the region of the less refrangible half of the spectrum. Spectroscopic examination also shows this. It has been suggested by Buller that these colouring matters may serve a useful purpose by screening off certain of the sun's rays from the living protoplasm. Spore-coloration may, however, depend, partly at least, upon the kind of substratum on which the fungi grow.

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