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The mode of growth of the Coniferae recalls a feature of the Equisetaceae also, in the tufts of little leaves which appear in whorls at regular intervals along the length of the stem in proportion as it elongates, reminding one of the articulations on the stem of the Equisetaceae.
For instance, in the Carboniferous period we have only Cryptogams, Ferns, Lycopodiacae, and Equisetaceae. In the middle geological ages, Conifers are introduced, the first flowering plant known on earth, but in which the flower is very imperfect as compared with those of the higher groups.
Vegetation of the Coal Period. Ferns, Lycopodiaceae, Equisetaceae, Sigillariae, Stigmariae, Coniferae. Angiosperms. Climate of the Coal Period. Mountain Limestone. Marine Fauna of the Carboniferous Period. Corals. Bryozoa, Crinoidea. Mollusca. Great Number of fossil Fish. Foraminifera.
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.
To this family belong two fossil genera of the coal, Equisetites and Calamites. They grew in dense brakes on sandy and muddy flats in the manner of modern Equisetaceae, and their remains are frequent in the coal. Asterophillites foliosus. Dawson, its foliage is distinguished by a true mid-rib, which is wanting in the leaves known to belong to some Calamites. Carruthers to be leaves of Calamites.
The first cone also appears on the summit of the stem, like the terminal cone in the Equisetaceae and the Club-Mosses. Thus in certain types of the vegetable, as well as the animal creation of earlier times, there was a continuation of features, afterwards divided and presented in separate groups.
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