"Fibrous Sigillaria."
(Rhytidolepis fibrosa, of Artis.)
Stems more or less flattened, with the external surface longitudinally furrowed, and uniformly ornamented with rows of deeply imprinted symmetrical figures, disposed with much regularity, are among the most abundant vegetable remains in the coal formation. These are named Sigillariæ, from the Latin word sigillum, signifying a seal, in allusion to the extreme regularity of the imprints on the surface. When found in an upright position, at right angles to the plane of the stratum, the original cylindrical form of the tree is commonly preserved; and many examples are now known of groups of erect Sigillariæ, with their roots extending into the surrounding clay or sandy loam; the roots proving to be the fossil bodies called Stigmariæ, which were formerly supposed to be a distinct family of aquatic plants.[16] The first discovery of this highly interesting and unexpected fact was made by Mr. Binney.[17]
[16] Dr. Buckland's Bridgewater Essay, vol. i. p. 476.
[17] See "Supplementary Notes, [p. 198]."
The specimen figured was found in an erect position in the sandstone of a quarry at Rowmarsh, near Rotherham in Yorkshire.
The stem is simple, the furrows small and wavy, impressed with dots on the ridges. The cicatrices are ovate, subpentagonal, with the lower angles rounded, having a single gland near the lower extremity. The stem is three feet long, and four inches in diameter.
The transverse section, as seen in fig. 1, shows traces of a double concentric ring, as if produced by internal structure. Fig. 2, displays the equality of the stem throughout its entire length, and its abrupt termination. In fig. 3, is seen the cicatrix with its single gland, for the attachment of the petiole or leaf-stalk. Fig. 4, indicates the undulating line of the top of the ridge.
"The originals of these fossils are supposed by M. Ad. Brongniart to have constituted a peculiar family of coniferous plants, now extinct, which probably belonged to the great division of gymnospermous dicotyledons. In their external forms they somewhat resembled the Cacteæ or Euphorbiæ, but were more nearly related by their internal organization to the Zamiæ or Cycadeæ. The leaves and fruits of these trees are unknown, for no satisfactory connexion has been established between the stems, and the foliage and seed vessels with which they are sometimes collocated."[18]
[18] Medals of Creation, vol. i. p. 138.