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There is room for astonishment when we consider the fact that the fossil representatives of the family, known as Lepidodendra, attained a height of no less than fifty feet, and, there is good ground for believing, in many cases, a far greater magnitude. They consist of long straight stems, or trunks which branch considerably near the top.
The reproductive bodies of the great Lepidodendra are sometimes more like seeds than spores, while both the wood and the leaves of the Sigillaria have features which properly belong to the Phanerogam. Further, it is now believed that a large part of what were believed to be Conifers, suddenly entering from the unknown, are not Conifers at all, but Cordaites.
They were invariably flattened to the thickness of one or two inches, and converted into coal. Their roots formed part of a stratum of coal ten inches thick, which rested on a layer of clay two inches thick, below which was a second forest resting on a two-foot seam of coal. Five feet below this, again, was a third forest with large stumps of Lepidodendra, Calamites, and other trees.
The lepidodendra bore linear one-nerved leaves, and the stems always branched dichotomously and possessed a central pith. Specimens variously named knorria, lepidophloios, halonia, and ulodendron are all referable to this family. Lepidodendron longifolium.
The Lepidodendra were shrubs and trees which put one more in mind of an Araucaria than of any other familiar plant; and the ends of the fruiting branches were terminated by cones, or catkins, somewhat like the bodies so named in a fir, or a willow.
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.
Many specimens of this family are found in the coal beds; it is thought they have contributed more to the substance of the coal than any other family. But, like the ferns and equisetaceae, they rise to a prodigious magnitude. In the forests of the coal era, the lepidodendra would enjoy the rank of firs in our forests, affording shade to the only less stately ferns and calamites.
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.
That particular tree was concluded to be an araucaria, a species now found in Norfolk Island, in the South Sea, and in a few other remote situations. The coniferae of this era form the dawn of dicotyledenous trees, of which they may be said to be the simplest type, and to which, it has already been noticed, the lepidodendra are a link from the monocotyledons.
All doubt was, however, finally dispelled by the discovery by Mr Binney, of a sigillaria and a stigmaria in actual connection with each other, in the Lancashire coal-field. Stigmariae have since been found in the Cape Breton coal-field, attached to Lepidodendra, about which we have already spoken, and a similar discovery has since been made in the British coal-fields.
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