of many of them must have been fifty or sixty feet, at least.* Count Sternberg has applied the name Syringodendron to many species of Sigillaria, from the parallel pipe-shaped flutings that extend from the top to the bottom of their trunks. These trunks are without joints, and many of them attain the size of forest trees. The flutings on their surface bear dot-like, or linear impressions, of various figures, marking the points at which the leaves were inserted into the stem. This fluted portion of the Sigillariæ, formed their external covering, separable like true bark from the soft internal axis, or pulpy trunk; it varied in thickness from an inch to one-eighth of an inch, and is usually converted into pure coal. (See Pl. 56, Fig. 2. a, b, c.) A fleshy trunk surrounded and strengthened only by such thin bark, must have been incapable of supporting large and heavy branches at its summit. It therefore probably terminated abruptly at the top, like many of the larger species of living Cactus, and the abundant disposition of small leaves around the entire extent of the trunk seems to favour this hypothesis. *M. Ad. Brongniart found in a coal mine in Westphalia near Essen, the compressed stem of a Sigillaria laid horizontally, to the length of forty feet; it was about twelve inches in diameter at its lower, and six inches at its upper extremity, where it divided into two parts, each four inches in diameter. The lower end was broken off abruptly. Lindley and Hutton's Foss. Flora, vol. i. p. 153. The impressions, or scars, which formed the articulations of leaves on the longitudinal flutings of the trunks of Sigillariæ, are disposed in vertical rows on the centre of each fluting from the top to the bottom of the trunk. Each of these scars marks the place from which a leaf has fallen off, and exhibits usually two apertures, by which bundles of vessels passed through the bark to connect the leaves with the axis of the tree. No leaf has yet been found attached to any of these trunks; we are therefore left entirely to conjecture as to what their nature may have been. This non-occurrence of a single leaf upon any one of the many thousand trunks that have come under observation, leads us to infer that every leaf was separated from its articulation, and that many of them perhaps, like the fleshy interior of the stems, had undergone decomposition, during the interval in which they were floating between their place of growth, and that of their final submersion. M. Ad. Brongniart enumerates forty-two species of Sigillaria, and considers them to have been nearly allied to arborescent Ferns, with leaves very small in proportion to the size of the stems, and differently disposed from those of any living Ferns. He would refer to these stems many of the numerous fern leaves of unknown species, which resemble those of existing arborescent genera of this family. Lindley and Hutton shew strong reasons for considering that Sigillariæ were Dicotyledonous plants, entirely distinct from Ferns, and different from any thing that occurs in the existing system of vegetation.* Favularia. Megaphyton. Bothrodendron. The same group of fossil plants to which Lindley and Hutton have referred the genus Sigillaria, contains four other extinct genera, all of which exhibit a similar disposition of scars arranged in vertical rows, and indicating the places at which leaves, or cones, were attached to the trunk. The names of these are Favularia, Megaphyton, Bothrodendron, Ulodendron.‡ Our figures Pl. 56, Figs. 3, 4, 5, 6, represent portions of "There can be no doubt," say they, (Foss. Flora, vol. i. p. 155) that as far as external characters go, Sigillaria approached Euphorbia and Cacteæ more nearly than any other plants now known, particularly in its soft texture, in its deeply channelled stems, and what is of more consequence in its scars, placed in perpendicular rows between the furrows. It is also well known that both these modern tribes, particularly the latter, arrive even now at great stature; further, it is extremely probable, indeed almost certain, that Sigillaria was a dicotyledonous plant, for no others at the present day have a true separable bark. Nevertheless, in the total absence of all knowledge of the leaves and flowers of these ancient trees, we think it better to place the genus among other species, the affinity of which is at present doubtful.” † Pl. 56, Figs. 3. 4. 5. 6. 7. The genera composing this group are thus described, Foss. Flora, vol. ii. p. 96. 1. Sigillaria. Stem furrowed. Sears of leaves small, round, much narrower than the ridges of the stem. the trunk and scars of some of these extraordinary Coniferæ. Among existing vegetables, there are only a few succulent plants which present a similar disposition of leaves, one exactly above another in parallel rows; but in the fossil Flora of the Coal 2. Favularia. Stem furrowed. Scars of leaves small, square, as broad as the ridges of the stem. 3. Megaphyton. Stem not furrowed, dotted. Scars of leaves very large, of a horse shoe figure, much narrower than the ridges. 4. Bothrodendron. Stem not furrowed, covered with dots. Scars of cones, obliquely oval. 5. Ulodendron. Stem not furrowed, covered with rhomboidal marks. Scars of cones circular. In the three first genera of this group, the scars appear to have given origin to leaves; in the two latter they indicate the insertion of large cones. In the genus Favularia (Pl. 56, Fig. 7) the trunk was entirely covered with a mass of densely imbricated foliage, the bases of the leaves are nearly square, and the rows of leaves separated by intermediate grooves; whilst in Sigillaria the leaves were placed more loosely, and at various intervals in various species. (Foss. Flora, Pl. 73. 74. 75). In the genus Megaphyton the stem is not furrowed, and the leaf scars are very large, and resemble the form of horse shoes disposed in two vertical rows, one on each side of the trunk. The minor impressions resembling horse shoes, in the middle of these scars, appear to indicate the figure of the woody system of the leaf stalk. (Foss. Flora, Pl. 116, 117.) In the genus Bothrodendron (Foss. Flora, Pl. 80, 81) and the genus Ulodendron, (Foss. Flora, Pl. 5. 6.) the stems are marked with deep oval or circular concavities, which appear to have been made by the bases of large cones. These cavities are ranged in two vertical rows, on opposite sides of the trunk, and in some species are nearly five inches in diameter. (Pl. 56. figs. 3. 4. 5. 6.) formation, nearly one half, out of eighty known species of Arborescent plants, have their leaves growing in parallel series. The remaining half are Lepidodendra, or extinct Coniferæ. (See Lindley and Hutton, Foss. Flora, vol. ii. p. 93.) Stigmaria.* The recent discoveries of Lindley and Hutton have thrown much light upon this very extraordinary family of extinct fossil plants. Our figure, Pl. 56, Fig. 8, copied from their engraving of Stigmaria ficoides, (Foss. Flora, Pl. 31, Fig. 1) represents one of the best known examples of the genus.† The centre of the plant presents a dome-shaped trunk or stem, three or four feet in diameter, the substance of which was probably yielding and fleshy; both its surfaces were slightly corrugated, and covered with indistinct circular spots. (Pl. 56, Fig. 8. 9.) From the margin of this dome there proceed many horizontal branches, varying in number in different individuals from nine to fifteen; some of these branches become forked at unequal distances from the dome; they are all broken off * Pl. 56, Fig. 8. 9. 10. 11. + Seventeen specimens of this kind have been found within the space of 600 square yards, in the shale covering the Bensham seam of coal at Jarrow Colliery near Newcastle, at the depth of 1200 feet. |