Fig. 45 b.
Fig. 45. a, Calamites Suckovii, composed of jointed striated fragments having a bark. Fig. 45. b, Septum or phragma of a Calamite.
Calamites (κάλαμος, a reed) is a reed-like fossil, having a sub-cylindrical jointed stem (Fig. 45, a and b; Fig. 46; [Plate IV. Fig. 4]). The stem is often crushed and flattened, and was originally hollow. Calamites is thus defined by Grand d'Eury (Ann. Nat. Hist. ser. 4, vol. iv. p. 124):—Stem articulated, fistular, and septate; outer part comparatively thin, formed of three concentric zones—1, an exterior cortical layer now converted into coal; 2, a thin subjacent zone of vascular tissue, now invariably destroyed; 3, a sort of inner lining epidermis, which is carbonified. Cortical envelope marked interiorly with regular flutings, interrupted and alternate at the articulations. Inner epidermis smooth, or scarcely striated. Vascular cylinder thin; outer surface of bark more fully fluted and articulated than the inner surface.
Fig. 46.
Fig. 46. Vertical stems of fossil trees, Calamites chiefly, found in the coal-measures of Treuil, near Saint Etienne.
Carruthers gives the following description of the structure of a species of Calamite which he examined:—The stem was composed of a central medulla, which disappeared with the growth of the plant, surrounded by a woody cylinder, composed entirely of scalariform vessels, and a thin cortical layer. The medulla penetrated the woody cylinder by a series of regular wedges, which were continued, as delicate laminæ of one or two cells in thickness, to the cortical layer. The cells of those laminæ were not muriform; their longest diameter was in the direction of the axis. The wedges were continuous, and parallel between each node. As the axial appendages were produced in whorls, the only interference with the regularity of the tissues was by the passing out through the stem at the nodes of the vascular bundles which supplied these appendages. As the leaves of each whorl were (with one or two exceptions) opposite to the interspaces of the whorls above and below, there was also at each node a re-arrangement of the wedges of vascular and cellular tissues.
Schimper considers Calamites as having an analogy with Equisetum in its fructification. He looks on them as fossil Equisetaceæ. Annularia and Sphenophyllum are considered as establishing a passage from the Equisetaceæ to the Lycopodiaceæ. Some gigantic fossil Equiseta had a diameter of nearly 5 inches, and a height of 30 or more feet. The branches, which adorned the higher part of them in the form of a crown, are simple, and have at their extremity a spike of the size of a pigeon's egg, and organised exactly like the spikes of living Equiseta. The subterranean rhizomes are well developed, and gave origin, like many Equiseta, to tubercles which had the form and size of a hen's egg.
The characters of Equisetum of the present day and Calamites, are exhibited in woodcut 47. They show a marked resemblance in the fructification. (See also [page 31].)