A Liasso-Rhaetic flora in South Wales

Abstract

A fossil flora is described from clay-filled fissures in the Carboniferous Limestone near Bridgend, South Wales. Nearly all the specimens belong to the conifer Cheirolepis muensteri. Most of them are charred fragments of various organs in which internal tissues are preserved. Cheirolepis was previously known from compressed German specimens yielding cuticles but no other tissues. The leaf is found to have a single vascular bundle and the wood is of somewhat Taxodiaceous structure but without xylem parenchyma. The bark produces thin scales of secondary phloem and cork. The male cone bears microsporophylls spirally; they are essentially dorsiventral and probably bear two pollen sacs only. The pollen is of unusual structure. The seed is orthotropous and the testa appears to be double. Other species are rare fragments of cuticle representing several Mesozoic genera and isolated spores, three of which have been determined. The age of the flora is between Rhaetic and Lower Liassic; it most resembles a flora in south-west Germany which is regarded as Lias $\alpha $. Reasons are put forward for supposing that the forest or scrub was burnt, and then the charred fragments were washed into water-courses in limestone fissures which soon after were submerged by the rising Liassic sea.