Lign. 68. Imprints of Dicotyledonous Leaves in Gypseous Marl.
Tertiary. Stradella, near Pavia.
| Fig. | 1.— | Leaf of Poplar (Populus græca). |
| 2.— | ———– Maple (Acer). | |
| 3.— | ———– Water-spike (Potamogeton). | |
| 4.— | ———– Willow (Salix). | |
| 5.— | ———– Chestnut (Æsculvs). |
The red marlstone associated with lignite in the plastic clay beds at Castle Hill, Newhaven (Geol. S. E. p. 54), contains leaves of a similar kind; a seed-vessel of a coniferous tree has also been found in it.
Some of the most interesting examples of dicotyledonous leaves that have come under my notice, are from the Sub-Apennine tertiary strata, at Stradella, near Pavia. They belong to several genera of arborescent, or at least ligneous plants, and most of them to species which still grow in Italy. In some examples the substance of the leaves is changed into carbon, and the structure well preserved; but, in general, sharp imprints on the stone are the only traces of the originals. They are found in a gypseous marl, of a cream colour; and, from their perfect state, it is inferred that they were enveloped in the soft matrix immediately after their fall, and preserved by the rapid crystallization of the gypsum. Two specimens from my cabinet are figured in Plate III. figs. 4 and 8; and outlines of a few other examples, in [Lign. 68].
Carpolithes (Fossil Fruits).—In the description of the fossil fruits from the Isle of Sheppey, several kinds of dicotyledons were included. Many species also abound in the lignites of Germany, France, and Italy; in those near Frankfort, seed-vessels of the Maple, Elm, Hornbeam, Birch, Willow, and Walnut, &c. In the environs of Turin, fruits of a species of Walnut (Juglans, [Lign. 67]), occur in the newer tertiary deposits, and are called Turin-nuts; the ligneous envelope has perished, but the form of its surface, and of the inclosed kernel, is preserved in calcareous spar. These nuts differ, both in the pericarp and kernel, from the living species: the lobes are simple ([Lign. 67, fig. 4b]), and not subdivided as in the common walnut; a species has been discovered at Lons-le-Saulnier, in which the lobes are mamillated.
Two kinds of fruits belonging to plants of the order Ranunculaceæ, and related to Thalictrum (Meadow-rue), have been found in the eocene deposits of France and England; one in the Paris basin, (meulière du terrain d'eau douce supérieur,) by M. Alexandre Brongniart, and the other in the Isle of Wight, by Mr. Webster. In the specimen from the last-named locality the pericarp is carbonized, and its cavity filled with clay. Figures of these seed-vessels are given in [Lign. 67, figs. 1, 2].
Carpolithes Smithiæ.—I would notice in this place some very remarkable fossil fruits that are occasionally met with in the White Chalk of Sussex and Kent, and appear to belong to dicotyledonous trees. The first specimen was discovered by me in a chalk-pit near Lewes, and is described in my "Fossils of the South Downs:" some illustrative examples collected by Mrs Smith, of Tunbridge Wells, tending to elucidate the nature of the original more satisfactorily than those in my collection, are figured and described by me in the Journal of the Geological Society, 1843, under the above name. These fruits are of an oval form, about one and a half inch long, and one inch wide, and are pressed almost flat. They are of a rich burnt-sienna colour, mottled with white, from the chalk having permeated their substance, and are studded over with slight eminences, which are the exposed summits of oblong flattened seeds. Although the internal structure is not preserved, there can be no doubt that the originals were spurious compound berries, having, like the Mulberry, the seeds imbedded in a soft pulpy mass.
FOSSIL DICOTYLEDONOUS TREES.
Fossil Dicotyledonous Trees.—The occurrence of trunks and branches of angiospermous trees in a carbonized state has already been described; like the monocotyledons and conifers, they also occur silicified.