Societies and Academies


    LONDON. Linnean Society, December 18.—E. J. Collins: The physiological aspect of the incidence of late blight (Phytophthora infestans) of potatoes. So far as the foliage is concerned, that of the early varieties of potato and those most susceptible to blight have the highest water content; the most resistant, which are the latest to mature, have the lowest water content. High water content induces rapid tuberisation, and this entails early maturation and susceptibility to blight. The nitrogen content of the foliage reaches a maximum and then falls more or less rapidly according to the growth period of the variety. Maturation is thus accompanied by a decreasing nitrogen content of the foliage. The water: nitrogen ratio increases during the season and in general is highest at the time of infection. The degree of susceptibility to blight is indicated more precisely by the value of this ratio. Young foliage has a lower water and higher nitrogen content than foliage of a medium age, while in old foliage the reverse conditions hold. Sprayed foliage shows a lower water and a higher nitrogen content than unsprayed foliage. The value of spraying, apart from the action of the copper solution as a fungicide, lies in its physiological effect, since those metabolic changes accompanying old age, and heightening susceptibility, are delayed.-R. B. Seymour Sewell: A study of the Andaman sea-basin. The Andaman Sea appears, originally, to have been formed during the Eocene epoch as a comparatively shallow brackish-water estuary, into which all the main rivers of Burma flowed, by the simultaneous upheaval of parallel mountain-ranges. At the close of the Miocene period a second upheaval, volcanic in character, caused the appearance of a mountain-chain that is now represented by Narcondam Island, Barren Island, and Invisible Bank. The present deep basin is due to extensive subsidence, probably in post-Tertiary times. Continued subsidence, or subaerial erosion followed by a rise of sea-level led to the formation of various channels permitting the entry into the basin of a shallow-water fauna derived from both the Indian and Pacific Oceans, and of a deep-water fauna derived from the Bay of Bengal.

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    Societies and Academies. Nature 115, 106–107 (1925).

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