In accordance with M. Brongniart’s generalisation, that the Palaeozoic period is, botanically speaking, the “Age of Acrogens,” we find the Carboniferous plants to be still mainly referable to the Flowerless or “Cryptogamous” division of the vegetable kingdom.  The flowering or “Phanerogamous” plants, which form the bulk of our existing vegetation, are hardly known, with certainty, to have existed at all in the Carboniferous era, except as represented by trees related to the existing Pines and Firs, and possibly by the Cycads or “false palms."[18] Amongst the “Cryptogams,” there is no more striking or beautiful group of Carboniferous plants than the Ferns.  Remains of these are found all through the Carboniferous, but in exceptional numbers in the Coal-measures, and include both herbaceous forms like the majority of existing species, and arborescent forms resembling the living Tree-ferns of New Zealand.  Amongst the latter, together with some new types, are examples of the genera Psaronius and Caulopteris, both of which date from the Devonian.  The simply herbaceous ferns are extremely numerous, and belong to such widely-distributed and largely-represented genera as Neuropteris, Odontopteris (fig. 108), Alethopteris, Pecopteris, Sphenopteris, Hymenophyllites, &c.

[Footnote 18:  Whilst the vegetation of the Coal-period was mainly a terrestrial one, aquatic plants are not unknown.  Sea-weeds (such as the Spirophyton cauda-Galli) are common in some of the marine strata; whilst coal, according to the researches of the Abbe Castracane, is asserted commonly to contain the siliceous envelopes of Diatoms.]

The fossils known as Calamites (fig. 109) are very common in the Carboniferous deposits, and have given occasion to an abundance of research and speculation.  They present themselves as prostrate and flattened striated stems, or as similar uncompressed stems growing in an erect position, and sometimes attaining a length of twenty feet or more.  Externally, the stems are longitudinally ribbed, with transverse joints at regular intervals, these joints giving origin to a whorl or branchlets, which mayor may not give origin to similar whorls of smaller branchlets still.  The stems, further, were hollow, with transverse partitions at the joints, and having neither true wood nor bark, but only a thin external fibrous shell.  There can be little doubt but that the Calamites are properly regarded as colossal representatives of the little Horse-tails (Equisetaceoe) of the present day.  They agree with these not only in the general details of their organisation, but also in the fact that the fruit was a species of cone, bearing “spore-cases” under scales.  According to Principal Dawson, the Calamites “grew in dense brakes on the sandy and muddy flats, subject to inundation, or perhaps even in water; and they had the power of budding out from the base of the stem, so as to form clumps of plants, and also of securing their foothold by numerous cord-like roots proceeding from various heights on the lower part of the stem.”