CAVAMITE, a genus of fossil plants whose true position has not been satisfactorily ascertained. They appear first in the Devonian rocks, and rise through the interme diate formations to the oolitic series, where they are represented by a single species. They reach their culminating point in the coal-measures, where 39 species have been determined. The tall straight stems rose from a swampy clay soil in profusion in the forests of sigillaria, and formed a striking and characteristic feature in the coal flora, though they supplied little material for the structure of coal. They are hollow-jointed cylinders, with longitudinal furrows, giving the fossil the appearance of equiseta; from this resemblance, botanists have generally considered them as huge "horsetails. " Hooker has been unable to detect any traces of structure, in carefully prepared speci mens, or the presence of those siliceous stomata which characterize equiseta, and which would have been preserved in the fossil state, and Fleming has shown that the furrows are markings on the interior cavity. While, therefore, it is certain that they are not
" horsetails," the absence of fructification makes every attempt to give them their posi tion but guess-work. Hooker supposes them nearly allied to ferns, or club-mosses; Brongniart ranks them among gymnospermous dicotyledons. The upper part of the stem, and the foliage, if any, have not been noticed. The root termination was conical, the joints decreasing downwards in size and length. From the scars on the upper portion of each joint, there proceeded filaments, which were supposed to be leaves, but are really roots. These are shown in the species figured—a species common in the English coal-field.