Equisetum Lyellii, [Lign. 12].—A species which I discovered in Wealden limestone, at Pounceford (Geol. S. E. p. 245), must have closely resembled the Equisetum fluviatile: it has an articulated cylindrical stem, and regularly dentated sheaths, embracing the stem at the joints.
A transverse slice of the stem exhibits under the microscope a cellular structure filled with calc-spar, and forms a beautiful object when viewed with the polarizing apparatus. This plant occurs in many localities of the Wealden in Sussex and Kent; from the railway cuttings near Tonbridge, I collected several fine specimens; it is met with also in the cliffs near Hastings.
Lign. 13. Equisetites columnaris.
(Ad. Brongn. Pl. 13.)
Lower Oolite. Whitby.
| Fig. | 1.— | Portion of a stem, showing two articulations, and an intermediate constriction. 1/3 nat. |
| 2.— | A few of the denticulations produced by the sheath, nat. |
Equisetites columnaris. [Lign. 13.]—A gigantic species of Equisetum abounds in the strata of the lower division of the Oolitic or Jurassic formation of Yorkshire, and many fine specimens have been collected, especially from the vicinity of Whitby. In the sandstone of the Inferior Oolite of the Cleveland Hills, Yorkshire, numerous stems of this colossal marestail have been observed standing erect, as if occupying the position in which they grew; the same fact was also discovered at Carlton Bank, near Stokesly, forty miles from the coast. In both localities fossil shells of fresh-water mussels (Uniones) were associated with the vegetable remains.
This plant is a true equisetum, differing chiefly from existing species in its gigantic size and arborescent character. The sheaths surrounding the stem, and the verticillate linear leaves, are preserved in some examples: and in all, the furrows left by the imprints of the sheaths are more or less strongly impressed. The stem is not channelled throughout, as in Calamites, the carboniferous plant whose stems at first sight might be mistaken for those of Equisetites, but which are entirely distinct, as will be explained hereafter. The Equisetites columnaris is peculiar to the Oolite; it does not occur in the coal-measures. Specimens have been discovered which indicate a height of twenty feet, and a diameter of several inches.[76]
[76] See Hist. Vég. Fossiles, p. 115.
A small species of Equisetum (Eq. Brodiei[77]) occurs in the insectiferous limestone of the lower Lias, at Strensham, Worcestershire, associated with the foliage of fresh-water endogenous plants resembling the Potamogeton, or pond-weed, and of supposed dicotyledonous vegetables.