T H E Members having assembled in the pu blic gallery of the Department , Mr. Ca rruthers began by pointing out that if, for palreontological purposes, we divided plants into cellular and vascular, we found that, as cellular tissues were th e first to disappear when plants decayed in water, so the cellular plan ts, the Fungi, Algse and Mosses, of which he had spoken on previous occa sions, were th e most liabl e to leave no traces of their existe nce. In the vasc ular plants, the lect urer

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... nued, which were far better represe n ted in a fossil state, a different iation of tissues had taken place, an d there were presen t an inte rna l skel eto n and an epiderma l layer, both capable of resist ing d ecay. T he chief existing grou ps were the EQUISETACEJE or horsetails, the FILICES or ferns, and the LVCOPODIACEJE, which three groups were "isosporous," i.e. having spores of one form onl y, and th e SELAGINELL-ACEJE, which were "heterosporous," i.e. having spores of two kinds. In the vascular Cryptogams th ere was an "alternation of generations:" the spo re, which was asex ual and bo rn e on the leaves of th e plant, on germination produce d structures bea ring either antheridia or arc hegonia (the male and female organs) or bo th; then th e arc hego nium on fertilisati on gave rise to a plan t like the parent which prod uced th e spo res. Among the vascular plants the EQUISETACEJE were apparently th e lowest group . Their sexua l stage was incon spicuous and th e spore -bea ring stage was the well-known" horse-tail." This had a hollow-jointed ste m bea ring branches in who rls; its fruit was in terminal cone s composed of peltate scale s, and its spo res were furnished with three coats, the outer one split into a coiled-up thread that was remarkably hygrometric and known as th e "elaters." Before Upper Silur ian tim es the re was no distinct record of land vegetation ; and it was in the De vonian th at th e earliest known lan d flora occurred. T his include d Equisctacere in which both vegetative and reproductive systems had a larger and more deve loped st ructure th an in our own existing gen us Equisetu 11I. These had bee n largely worked out by P rof. \Y. C. Williamson in various memoirs, of which that on Hommannites in the 'Philosophical T ran saction s ' was one of the mos t important. The