Figs. 30 to 32. Stem of Tree-ferns, called Caulopteris. Fig. 30. Caulopteris macrodiscus. Fig. 31. Caulopteris Balfouri (Carr.), Coal-measures. Fig. 32. Caulopteris Morrisi (Carr.), Coal-measures.
The rarity of Tree-ferns in the coal-measures has often been observed, and it is the more remarkable from the durable nature of their tissues. Several species have, however, been noticed. They are referred to the genus Caulopteris. One of them, C. macrodiscus (Fig. 30) has the leaf-scars in linear series. Two other species are figured, the one a slender form with the scars widely separated, as in some Alsophilas, C. Balfouri (Fig. 31) from the Somersetshire coal-field; and the other with larger stems and more closely aggregated scars, C. Morrisi (Fig. 32), from the coal-measures at Newcastle. The latter species shows the cavities at the base of the petiole described by Mohl in many living fern-stems. The fossils named Psaronius appear to have been fern-stems with a slender axis and a large mass of adventitious roots, as in some Dicksonias and in Osmunda regalis. These stems probably belong to some of the fronds to which other names are given, but as they have not been found attached, it is impossible to determine the point. Miller has described a fern as occurring in the coal-measures, which at first sight presents more the appearance of a Cycadaceous frond than any other vegetable organism of the carboniferous age except the Cycadites Caledonicus (Salter), from Cockburnspath Cove. He thus describes it:—
"From a stipe about a line in thickness there proceed at right angles, and in alternate order, a series of sessile lanceolate leaflets, rather more than two inches in length, by about an eighth part of an inch in breadth, and about three lines apart. Each is furnished with a slender midrib; and, what seems a singular, though not entirely unique feature in a Fern, the edges of each are densely hirsute, and bristle with thick short hair. The venation is not distinctly preserved."
Fig. 33. Fig. 34.
Fig. 36. Fig. 37.
Figs. 33 to 37 exhibit forms of Sigillaria stems found in the shales of the Carboniferous epoch. Fig. 33. Stem of Sigillaria pachyderma in an erect position, covered by successive deposits of sandstone and shale; one of the stems is bifurcated. Fig. 34. Sigillaria reniformis, with its external markings, and roots which are Stigmarias, as proved by Mr. Binney. Fig. 35. Sigillaria pachyderma, after Lindley and Hutton, from the shale of Killingworth Colliery, showing the scars or places through which the vessels of the stem passed to the leaves. Fig. 36. Sigillaria (Favularia) tessellata, from the Denbigh coal-shale, showing the fluted stem with scars. Fig. 37. Sigillaria pachyderma; the stem marked with scars, and fluted longitudinally.
Fig. 35.