The genus sigillaria, one of the most common of the coal plants, possessed the singular properties of being apparently hollow in the center, yet with an inner woody axis floating in a woody succulent jelly, and inclosed in a thick outer coating of bark. The trunk is beautifully fluted with longitudinal parallel lines, regularly arranged along the surface, and dotted all over with small scars, as if impressed by the leaves penetrating through the bark into the central woody axis. The stigmariæ, once supposed to be a distinct genus, are now generally regarded as simply the roots of the sigillariæ; they are, for the most part, found resting in their natural position, in large clusters often; and forming with their dense matted fibers a floor of considerable thickness, on which, season after season, the leaves fell as the coaly matter accumulated. This tree grew to an enormous size, specimens of four feet in diameter by fifty feet in length being frequently met with; traces of a vascular and fibrous structure can be observed in the stems—also the annular wood layers are sometimes beautifully defined; and, combined with a coating of bark of an inch in thickness, the probability is, that the sigillaria belonged to the exogenous class of vegetables. [Illustration: Calamite.] But of all the plants found in the coal-measures, the CONIFERÆ or pine tribe, distinguished by their punctated woody tissue, are the most interesting, whether we consider their characteristic properties, extensive distribution, antiquity, and consistency of habit through all the epochs and changes of creation. Unlike the tree-forms already noticed, the pines grow now as they grew before, inhabiting the same places, and preserving the same appearances in bulk and figure. In structure the coniferæ occupy a place intermediate between cellurares and vasculares, connected with the former through the lycopodiums, and with the latter by the myriceæ, or aromatic gale tribe. The scales of the cones are regarded by botanists as true foliage or reduced leaves, and in this respect they approximate to the genus zamia, of the order cycadeæ, where these organs are distinctly developed as carpellary leaves. Thus widely connected through the chain of vegetable life, the fossil pines, discovered in our coal-fields, form also the most interesting link between the present and the remote past, showing similar conditions of vegetable existence and forest landscape. No class of plants have been more useful to man than the whole pine family; none are more universal in their distribution over the face of the globe; none are possessed of such powers of endurance, existing through all time, and natives of every part of the world, from the perpetual snows of Arctic America, to the hottest regions of the Indian Archipelago. These trees differ as remarkably in form as in size, ranging through every gradation from the stinted juniper of the Grampians to the stately cedars of Lebanon. And