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Returning to the more special subject of this work, I may remark that the lepidodendroid trees and the ferns, both the arborescent and herbaceous kinds, are even more richly represented in the Carboniferous than in the preceding Erian. I must, however, content myself with merely introducing a few representatives of some of
the more common kinds, in an ap
pended note, and 1
here give a figure of a well-known Lower Carboniferous lepidodendron, with its various forms of leaf-bases,
and its foliage and 5
fruit (Fig. 43), and a similar illustration of an allied generic form, that
known as Lepido7
phloios * (Fig. 44). FIG. 41.-Beds associated with the main coal
Another group (S. Joggins, Nova Scotia). 1, Shale and sandstone-plants with Spirorbis attached; rain- which claims our marks (?). (2,, Sandstone and shale, eight feet-erect Calamites ; 3, Gray sandstone, attention is that seven feet; 4, Gray shale, four feet-an erect coniferous (?) tree, rooted on the shale, passes
of the Calamites. up through fifteen feet of the sandstones and These are tall, cyshale.) 5, Gray sandstone, four feet. 6, Gray shale, six inches-prostrate and erect trees, lindrical, branchwith rootlets, leaves, Naiadites, and Spirorbis on the plants. 7, Main coal-seam, five
less stems, with feet of coal in two seams. 8, Underclay, with whorls of branchrootlets.
lets, bearing needlelike leaves and spreading in stools from the base, so as to form dense thickets, like Southern cane-brakes (Fig. 46). They bear, in habit of growth and fructification, a close
* For full descriptions of these, see “ Acadian Geology."
relation to our modern equisetums, or mare's-tails, but, as in other cases we have met with, are of gigantic size and comparatively complex structure. Their stems, in cross-section, show radiating bundles of fibres, like those of exogenous woods, yet the whole plan of structure presents some curious resemblances to the stems of their humble successors, the modern mare's-tails. It would seem, from the manner in which dense brakes of these Calamites have been preserved in the coal-formation of Nova Scotia, that they spread over low and occasionally inundated flats, and formed fringes on the seaward sides of the great Sigilla- FIG. 42.-Erect Sigillaria, standing ria forests. In this way
on a coal-seam (s. Joggins, Nova
Scotia). they no doubt contributed to prevent the invasion of the areas of coal accumulation by the muddy waters of inundations, and thus, though they may not have furnished much of the material of coal, they no doubt contributed to its purity. Many beautiful plants of the genera Asterophyllites and Annularia are supposed to have been allied to the Calamites, or to have connected them with the Rhizocarps. The stems and fruit of these plants have strong points of resemblance to those of Sphenophyllum, and the leaves are broad, and not narrow and angular like those of the true Calamites (Fig. 45).
No one has done more than my friend Dr. William
FIG. 43.— Lepidodendron corrugatum, Dawson, a tree characteristic of the
Lower Carboniferous. A, Restoration. B, Leaf, natural size. c, Cone and branch. D, Branch 'and leaves. 2, Various forms of leaf-areoles. F, Sporangium. I, 1, m, Bark, with leaf-scars. N, Bark, with leafscars of old stem. 6, Decorticated stem (Knorria).
FIG. 44.- Lepidophloios Acadianus, Dawson, a lepidodendroid tree of the
coal-formation. A, Restoration. B, Portion of bark (two thirds natural size). o, Ligneous surface of the same. F, Cone (two thirds natural size), G, Leaf (natural size). K, Portion of woody cylinder, showing outer and inner series of vessels magnified. L, Scalariform vessels (highly magnified). M, Various forms of leaf-scars and leaf-bases (natural size).
son, of Manchester, to illustrate the structure of Calamites, and he has shown that these plants, like other cryptogams of the Carboniferous, had mostly stems with regular fibrous wedges, like those of exogens. The structure of the stem is, indeed, so complex, and differs so much in different stages of growth, and different states of preservation, that we are in danger of falling into the greatest confusion in classifying these plants. Sometimes what we call a Calamite is a mere cast of its pith showing longitudinal striæ and constrictions at the nodes. Some
Fig. 45.- Asterophyllites, Sphenophyllum, and Annularia. A, Astera
phyllites trinerne. Al, Leaf enlarged. 'B, Annularia sphenophylloides. B!, Leaf enlarged. , Sphenophyllum erosum. C!,, Leaflet enlarged. 02, Scalariform vessel 'of Sphenophyllum. D, Pinnúlaria ramosissima, probably a root.
times we have the form of the outer surface of the woody cylinder, showing longitudinal ribs, nodes, and marks of the emission of the branchlets. Sometimes we have the outer surface of the plant covered with a smooth bark showing flat ribs, or almost smooth, and having at the nodes regular articulations with the bases of the verticil