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podiaceae and Coniferae. Together with these, there occur other groups of Plants unknown in modern vegetation, and of which the duration seems to have been limited to the Epochs of the Transition Period. Among the largest and tallest of these unknown forms of Plants, we find collossal Trunks of many species, which M. Ad. Brongniart has designated by the name of Sigillaria. These are dispersed throughout the sand-stones and shales that accompany the Coal, and can occasionally be detected in the Coal itself, to the substance of which they have largely contributed by their remains. They are sometimes seen in an erect position, where views of the strata are afforded by cliffs on the sea shore, or by inland sections of quarries, banks of rivers, &c*

* On the coast of Northumberland, at Creswell hall, and Newbiggin, near Morpeth, many stems of Sigillaria may be seen, standing erect at right angles to the planes of alternating strata of shale and sand-stone; they very from ten to twenty feet in height, and from one to three feet in diameter, and are usually truncated at their upper end; many terminate downwards in a bulb-shaped enlargement, near the commencement of the roots, but no roots remain attached to any of them. Mr. W. C. Trevelyan counted twenty portions of such Trees, within the length of half a mile; all but four or five of these were upright; the bark, which was seen when they were first uncovered, but soon fell off, was about half an inch in thickness, and entirely converted into coal. Mr. Trevelyan observed four varieties of these stems, and engraved a sketch of one of them in 1816, which is copied in Count Sternberg's Table 7. Fig. 5.

In September, 1834, I saw in one of the Coal Mines of Earl Fitzwilliam, at Elseear, near Rotherham, many large Trunks of Sigillaria, in the sides of a gallery by which you walk into the mine, from the outcrop of a bed of Coal about six feet thick. These stems were inclined in all directions, and some of them nearly vertical. The interior of those whose inclination exceeded 45° was filled with an indurated mixture of clay and sand; the lower extremity of several rested on the upper surface of the bed of Coal. None had any traces of Roots, nor could any one of them have grown in its present place.

M. Alex. Brongniart has engraved a section at St. Eticnne, in which many similar stems are seen in an erect position, in sand-stone of the Coal formation, and infers from this fact that they grew on the spot where they are now found. M. Constant Provost justly objects to this inference, that, had they grown on the spot, they would all have been rooted in the same stratum, and not have had their bases in different strata. When I visited these quarries in 1826, there were other trunks, more numerous than the upright ones, inclined in various directions.

The vertical position of these trunks, however, is only occasional and accidental; they lie inclined at all degrees throughout all the strata of the carboniferous series; but are most frequently prostrate, and parallel to the lines of stratification, and, in this position are usually compressed. When erect, or highly inclined, they retain their natural shape, and their interior is filled with sand or clay, often different from that of the stratum in which their lower parts are fixed, and mixed with small fragments of various other plants. As this foreign matter has thus entirely filled the interior of these trunks, it follows that they must have been without any transverse dissepiments, and hollow throughout, at the time when the sand, and mud, and fragments of other plants found admission to their interior. The bark, which alone remains, and has been converted into coal, probably surrounded an axis composed of soft and perishable pulpy matter, like the fleshy interior of stems of living Cacteae; and the decay of this soft internal trunk, whilst the stems were floating in the water, probably made room for the introduction of the sand and clay.

These trunks usually vary from half a foot to three feet in diameter. When perfect, the height of many of them must have been fifty or sixty feet, at least.*

I have seen but one example, viz. that of Balgray quarry, three miles N. of Glasgow, of erect stumps of large trees fixed by their roots in sand-stone of the coal formation, in which, when soft, they appear to have grown, close to one another. See Lond. and Edin. Phil. Mag. Dec. 1835, p. -187.

* 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 st its upper extremity, where it divided into two parts, each four inches

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 Sigillariae, formed their external covering, separable like true bark from the soft internal axis, or pulpy trunk; it varied in thickness from an inch to oneeighth of an inch, and is usually converted into pure coal.. (See PI. 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.

The impressions, or scars, which formed the articulations of leaves on the longitudinal flutings of the trunks of Sigillariae, 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.

in diameter. The lower end was broken off abruptly. Lindley and Hutton's Fobs. Flora, vol. i. p. 153.

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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 lining 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 show reasons for considering that Sigillariae were Dicotyledonous plants, entirely distinct from Ferns, and different from any thing that occurs in the existing system of vegetation.*

Favularia. Megaphyton. Bothrodendron. Ulodendron.-f

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 indicatingthe 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 the trunk and scars of some of these extraordinary Coniferae.

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* "There can be no doubt," say they, (Foss. Flora, vol. i. p. 155) "that as far as external characters go, Sigillaria approached Euphorbia e and Cactcjc 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 ; farther, 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."

t PI. 56, Figs. 3.4. 5.6. 7..

^S

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 formation, nearly one-half, out of eighty known species of Arborescent plants, have their leaves growing in parallel series. The remaining half are Lepido

* The genera composing this group are thus described, Foss, Flora, vol. ii. p. 96.

1. Sigillaria. Stem furrowed. Scars of leaves small, round, much narrower than the, ridges of the stem. See PI. 56, Figs. 1, 2, 2'.

2. Favularia. Stem furrowed. Scars of leaves small, square, as broad as the ridges of the stem. See PI. 56, Fig. 7.

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. See PI. 56, Figs. 3, 4,5, 6, 6'.

In the first three genera of this group, the scars appear to have given origin to leaves; in the latter two ttley indicate the insertion of large cones.

In the genus Favnluria (PI. 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, PI. 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, PI. 116,117.)

In the genus Bothrodendron (Foss. Flora, PI. 80, 81) and the genus Ulodendron, (Foss. Flora, PI. 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 arc ranged in two vertical rows, on opposite sides of the trunk, and in some species are nearly five inches in diameter. (PI. 56. Figs. 3. 4. 5. 6.)

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