Page:Transactions of the Linnean Society of London, Volume 20.djvu/549

 shows, in the arrangement of its vascular bundles, a preparation for the supply of an equal number of bracteæ. These vascular fasciculi are nearly equidistant in a tissue of moderately elongated cells.

The vessels are exclusively scalariform, very closely resembling those of the recent Ferns and Lycopodiaceæ; and among fossils, those of Psarolites, Lepidodendron, and its supposed fruit, Lepidostrobus, as well as several other fossil genera; namely, Sigillaria, Stigmaria, Ulodendron, Halonia? and Diploxylon.

The coat of the sporangium appears to be double; the outer layer being densely cellular and opake, the inner less dense, of a lighter colour, and formed of cells but slightly elongated.

On the lower or adnate side of the sporangium this inner layer seems to be continued, in some cases at least, in irregular processes to a considerable depth. I cannot, however, find that the sporules are actually formed in this tissue, but in another of somewhat different appearance and form, of which I have been only able to see the torn remains.

The minute granular bodies which accompany the sporules in the drawing (XXIV), fig. G, are probably particles of the mother cells, and are neither uniform in size nor outline.

The whole specimen has suffered considerable decay or loss of substance, which is most obvious in the sporangia from their greater transparency, but equally exists in the opake bracteæ, in which radiating crystallization occupies the space of the removed cellular substance.

I cannot at present enter fully into the question of the affinities of Triplosporite. I may remark, however, that in its scalariform vessels it agrees with all the fossil genera supposed to be Acotyledonous. In the structure of its sporangia and sporules it approaches most nearly, among recent tribes, to Lycopodiaceæ, and Ophioglosseæ; and among fossils, no doubt, to Lepidostrobus, and consequently to Lepidodendron.

The stem structure of Lepidodendron, known to me only in one species, Lepidodendron Harcourtii, offers no objection to this view, the vascular arrangement of the axis of its stem bearing a considerable resemblance to that of Triplosporite. To the argument derived from an agreement in structure between axis of stem and of strobilus I attach considerable importance, an equal agreement existing both in recent and fossil Coniferæ.