The _Lycopods_ of our age are humble plants, scarcely a yard in height, and most commonly creepers; but those of the ancient world were trees of eighty or ninety feet in height. Their leaves were sometimes twenty inches long, and their trunks a yard in diameter. Such are the dimensions of some specimens which have been found. Another Lycopod of this period attained dimensions still more colossal. The _Sigillarias_ sometimes exceeded 100 feet in height. Herbaceous Ferns were also exceedingly abundant and grew beneath the shade of these gigantic trees. It was the combination of these lofty trees with the undergrowth of smaller vegetation which formed the forests of the Carboniferous period. "What could be more surprising," exclaims Figuier, "than the aspect of this exuberant vegetation, these immense trees, these elegant arborescent ferns with airy foliage, fine cut, like delicate lace. Nothing at the present day can convey to us an idea of the prodigious and immense extent of never-changing verdure which clothed the earth, from pole to pole, under the high temperature which everywhere prevailed over the whole terrestrial globe. In the depths of these inextricable forests parasitic plants were suspended from the trunks of the great trees, in tufts or garlands, like the wild vines of our tropical forests. They were nearly all pretty, fern-like plants, they attached themselves to the stems of the great trees, like the orchids of our times." The margin of the waters would also be covered with various plants with light and whorled leaves, belonging, perhaps, to the Dicotyledons. Before leaving the subject of the plants of the coal measures, we should perhaps mention as one of the most interesting discoveries of the present generation that whereas the links between the fern-like trees of those days and the cycads, or early group of seed-bearing plants, were for long missing, they have been found by the researches of Professor F. W. Oliver, F.R.S., who has identified in the _Lyginodendron_ a seed-bearing fern from the coal measures.