Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/394

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As the drifted seeds that occur in Sheppey seem to have been collected by the action of marine currents, the history of European vegetation during the Tertiary period, must be sought for in those other remains of plants, whose state and circumstances show that they have grown at no great distance from the spot in which they are now found.

The following is a summary of what is yet known, respecting the varying conditions of the Flora of the three great periods of Geological history we have been considering.

The most characteristic distinctions between the vegetable remains of these periods are as follows. In the first period, the predominance of vascular Cryptogamic, and comparative rarity of Dicotyledonous plants. In the second, the approximation to equality, of vascular Cryptogamic, and Dicotyledonous plants. In the third, the predominance of Dicotyledonous, and rarity of vascular Cryptogamic plants. Among existing vegetables almost two-thirds are Dicotyledonous.

The Remains of Monocotyledonous plants occur, though sparingly, in each Period of Geological formations.

The number of fossil plants as yet described is about five hundred; nearly three hundred of these are from strata of the Transition series; and almost entirely from the Coal formation. About one hundred are from strata of the Secondary series, and more than a hundred from formations of the