When the outer surface is preserved it is sometimes seen to bear verticils of long needle-like leaves (_C. Cistii_), or of branchlets with secondary whorls of similar leaves (_C. Suckovii_ and _C. undulatus_). No Calamite known to me bears broad one-nerved leaves like those of _Asterophyllites_ and _Annularia_, though the larger stems of these plants have been described as Calamites, and the term _Calamocladus_ has been used to include both groups. The base of the Calamite stem usually terminates in a blunt point, and may be attached to a rhizome, or several stems may bud out from each other in a group or stool. The roots are long and cylindrical, sometimes branching. The fruit consists of spikes of spore-cases, borne in whorls and subtended by linear floral leaves. To these strobiles the name Calamostachys has been given. Williamson has shown that the stem of Calamites consists of a central pith or cavity of large size surrounded by a cylinder consisting of alternate wedges of woody and cellular matter, with vertical canals at the inner sides of the wedges, and slender medullary rays. The thick cellular wedges intervening between the woody wedges he calls primary medullary rays; the smaller medullary rays in the wedges, secondary medullary rays. There is thus a highly complex exogenous stem based on the same principle with the stem of a common _Equisetum_, but with much greater strength and complexity. Williamson has also shown that there are different sub-types of these stems. More especially he refers to the three following: (_a_) _Calamites_ proper, which has the woody wedges of scalariform or barred tissue with thin medullary rays, and the thick primary medullary rays are cellular. (_b_) _Calamopitus_ has reticulated or multiporous tissue in the woody wedges with medullary rays, and the primary medullary wedges are composed of elongated cells. (_c_) _Calamodendron_ has the woody wedges of barred tissue as in _a_, with medullary rays, but has the intervening medullary wedges of an elongated tissue approaching to woody fibre, and also with medullary rays. To these I would add a fourth type, which I have described, from the coal-formation of Nova Scotia.[DB] [DB] "Quarterly Journal of the Geological Society," 1871. (_d_) _Eucalamodendron_ differs from _Calamodendron_ in having true bordered pores or pseudo-scalariform slit-pored tissue, and corresponds to the highest type of calamitean stem. I would also add that under _a_ and _b_ there are some species in which the woody cylinder is very thin in comparison to the size of the stem. In _c_ and _d_ the woody cylinder is thick and massive, and the stems are often large and nodose. As an example of an ordinary Calamite in which the external surface and foliage are preserved, I may quote the following from my report on the "Flora of the Lower Carboniferous and Millstone Grit," 1873: