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Updated: May 17, 2025
Whatever serious difficulty there ever was in this scantiness of intermediate types is amply met by the fact that every fresh decade of search in the geological tombs brings some to light. We have seen many instances of this the seed-bearing ferns and flower-bearing cycads, for example, found in the last decade and will see others.
Their family has come down practically unchanged from the steaming days of the Carboniferous period, when ferns grew one hundred feet high, and thronged with other rank tropical growths in matted masses to form the coal measures. The fossil remains of cycads in the rocks of that period prove that they once flourished in the tropic swamps where now are the hills of Wyoming and Dakota.
Cryptogamous acrogens: Acrogens: Mosses, equisetums, ferns, lycopodiums Lepidodendra. Dicotyledonous gymnosperms: Gymnogens: Conifers and Cycads. Dicotyledonous Angiosperms: Exogens: Compositae, leguminosae, umbelliferae, cruciferae, heaths, etc. All native European trees except conifers. Monocotyledons: Endogens.
The angiosperms seem, therefore, to have been at the least comparatively rare in these older secondary periods, when more space was occupied by the Cycads and Conifers. The entire group of Oolite and Lias consists of repeated alternations of clay, sandstone, and limestone, following each other in the same order.
Dense forests of tree ferns throve in moist regions, and canebrakes of horsetails of modern type, but with stems reaching four inches in thickness, bordered the lagoons and marshes. Cycads were exceedingly abundant.
But there is no ground for mystic speculation on this circumstance of a group of organisms fording the earth for a few million years, and then perishing or dwindling into insignificance. We shall see that a very plain and substantial process put an end to the Age of the Cycads, Ammonites, and Reptiles, and we have seen how the earlier dynasties ended.
On the other hand, the Bennettiteae of the Jurassic have the mixed characters of ferns, cycads, and flowering plants, and thus, in their turn, point downward to a lower ancestry and upward to the next great stage in plant-development. It is not suggested that the seed-ferns we know evolved into the cycads we know, and these in turn into our flowering plants.
Warren did as she was told. Vivie left her seated in one of the long series of glass houses overlooking Brussels from a terrace, wherein are assembled many glories of the tropics: palms, dracaenas, yuccas, aloes, tree-ferns, cycads, screw-pines, and bananas: promising to be back in an hour's time. Somehow as she sat there it seemed to Mrs.
Whatever the causes were, the earth has returned to paradisiacal conditions. The vast ice-fields have gone, the scanty and scrubby vegetation is replaced by luscious forests of cycads, conifers, and ferns, and warmth-loving animals penetrate to what are now the Arctic and Antarctic regions.
Though the roots of the Sigillaria bear more resemblance to the rhizomes of certain aquatic plants; yet, structurally, they are absolutely identical with the roots of Cycads, which the stems also resemble. Further, the Sigillarioe grew on the same soils which supported Conifers, Lepidodendra, Cordaites, and Ferns-plants which could not have grown in water.
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