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Societies and Academies

    Naturevolume 105pages346347 (1920) | Download Citation

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    LONDON. Royal Society, April 29.—Sir J. J. Thomson, president, in the chair.—Prof. J. W. Gregory: The Irish eskers. Eskers are banks of sand and gravel, typically occurring as ridges on the central plain of Ireland, where they were deposited during the recession of the ice at the close of the Glacial period. They have been generally attributed to deposition along glacial rivers, like Swedish osar. Their structure and composition indicate that the most important Irish eskers were formed along the margin of the receding ice-sheets by floods of water,due to the melting of the ice. Irish eskers formed along glacial rivers are relatively small and exceptional. The accumulation of the materials into ridges, and their restriction between about 150 ft. and 300 ft. above sea-level, are attributed to the formation of the eskers where the ice entered into a sheet of water, which was probably the sea, since marine fossils are widely distributed in the adjacent drifts, and there are no embankments to maintain glacial lakes at the required level. It is proposed that the term “esker” should be continued for Irish ridges and mounds of sand and gravel, but that in glacial geology theterm “osar” should be used for ridges formed along the course of glacial rivers, and “kame” for ridges deposited by water along the margin of an ice-sheet. Miss K. M. Curtis: The life-history and cytology of Synchytrium endobioticum (Schilb.), Perc, the cause of wart disease in potato. The life-history and cytology of the organism have been followed through all their stages. In the course of the investigation the following important points have beendetermined: (1) A sexual process has been discovered and followed in all its details; (2)the nature of the difference between the resting (or winter) sporangia and the sori (or summer sporangia) has been established; (3) the infection of the host-tissue by the zoospores and zygotes has been traced; and (4) the peculiarities in the behaviour of the nucleus of the parasite have been investigated.¢B. Sahni: The structure and affinities of Acmopyle pancheri, Pilger. Acmopyle, a monotypic New Caledonian Podocarp, is the most specialised member of the Podocarpineae, and closely allied to the genus Podocarpus, which it resembles in the vegetative anatomy, drupaceous seed, megaspore membrane, young embryo, structure of malecone, microsporophyll, pollen-grain, and probably male gametophyte. It differs from Podocarpus in (1) the nearly erect seed; (2) the complete fusion of the epimatium to the integument, even in the region of the micrbpyle, in the formation of which it takes part; and (3) the much greater development of the vascular system of the seed, which forms a nearly continuous cup-like tracheal investment covering the basal two-thirds of the stone, (a) The Taxineae are structurally so distinct from the remaining conifers as to justify their being placed in a separate phylum, Taxales, equivalent in rank, and related to, the Ginkgoales arid the Coniferales as here defined. The Cordaitalean affinities of the Taxales are emphasised, (b) Concerning the ovuliferous scale of the conifers, the conclusion is in favour of the brachyblast theory, support for this view being derived from the structure of the megastrobilus of Acmopyle. (c) No definite opinion is expressed on the question whether the conifers arose ultimatelv from microphyllous or megaphyllous ancestors, for the origin of the Cordaitales themselves is still regarded as sub judice.

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    https://doi.org/10.1038/105346a0

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