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Updated: June 3, 2025
Gymnosperms, akin to the cycads, were also present in the Carboniferous forests. Such were the different species of CORDAITES, trees pyramidal in shape, with strap-shaped leaves and nutlike fruit. Other gymnosperms were related to the yews, and it was by these that many of the fossil nuts found in the Coal Measures were borne.
Further, the Sigillariae grew on the same soils which supported Conifers, Lepidodendra, Cordaites, and Ferns plants which could not have grown in water. Again, with the exception perhaps of some Pinnulariae and Asterophyllites, there is a remarkable absence from the coal measures of any form of properly aquatic vegetation.
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.
When reduced to thin, transparent plates, these latter show us the organization of the wood of Arthropitus, Cordaites, and Calamodendron, and of the petioles of Aulacopteris, that is to say, of the ligneous and arborescent plants that we most usually meet with in the coal measures of Commentry in the state of impression or of coal.
Dawson, "consists principally of the flattened bark of Sigillarioid and other trees, intermixed with leaves of Ferns and Cordaites, and other herbaceous débris, and with fragments of decayed wood, constituting 'mineral charcoal, all these materials having manifestly alike grown and accumulated where we find them."
Like the birds and mammals they await the coming of a fresh period of cold to give them a decided superiority over the cycads. Botanists look for their ancestors in some form related to the Cordaites of the Coal-forest. The ginkgo trees seem to be even more closely related to the Cordaites, and evolved from an early and generalised branch of that group.
The Cordaites is a very remarkable combination of features that are otherwise scattered among the Cryptogams, Cycads, and Conifers. On the other hand, a very large part of what the geologist had hitherto called "Ferns" have turned out to be seed-bearing plants, half Cycad and half Fern. This earlier stage is lost in those primitive ages from which not a single leaf has survived in the rocks.
A thin section of a piece of Commentry cannel coal shows that this substance consists of a yellowish-brown amorphous mass holding here and there in suspension very different plant organs, such as fragments of Cordaites, leaves, ferns, microspores, macrospores, pollen grains, rootlets, etc., exactly as would have done a gelatinous mass that upon coagulating in a liquid had carried along with it all the solid bodies that had accidentally fallen into it and that were in suspension.
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.
The familiar fossil known to geologists as Sternbergia has now been shown to be the cast of the central pith of these conifers, amongst which may be mentioned cordaites, araucarites, and dadoxylon.. The central cores had become replaced with inorganic matter after the pith had shrunk and left the space empty.
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