| Woody fibres. | Medullary rays and pith. | Generic names. | Geological age. | ||
| No discs. | One or two series of cells. | Aporoxylon, Unger. | Devonian (Erian). | ||
| Discs in one series contiguous, or in several series spirally arranged. | Complex, or of two or more series of cells. Pith Sternbergian. |
| Middle and Lower Carboniferous and Devonian. | ||
| Simple, or of one row of cells. Pith Sternbergian. |
| Upper Carboniferous and Permian. | |||
| Pith in spherical chambers. | Ormoxylon,[CQ] Dn. | Devonian. | |||
| Medullary sheath scalariform. Medullary rays frequent, simple, short. | Dadoxylon (Cordæoxylon),[CR] Dn. | Devonian. |
[CQ] Type O. Erianum, Dn., “Report on Canadian Plants,” 1871.
[CR] Type D. Clarkii, Dn., “Report on Canadian Plants,” 1882. This may be wood of Cordaites, to which it approaches very closely.
Family Cordaites, Genus Cordaites, Brongniart.
Trunks marked by transverse scars of attachment of bases of leaves; leaves broad, with many parallel veins, and attached by a broad base; pistillate and staminate catkins of the nature of Antholithes. Fruit winged or pulpy, of the kind known as Cardiocarpum. Stem with a Sternbergia pith, usually large, surrounded by a ring of pseudo-scalariform vessels, and with a cylinder usually narrow, of woody wedges, with bordered pores in one or more series, and with simple medullary rays.
From specimens kindly presented to me by Prof. Renault, I have been able to ascertain that the stems of some at least of these plants (Eucordaites) are distinct in structure from all the species of Dadoxylon, above mentioned, except D. Clarkii, of the Erian. They may be regarded as intermediate between those of conifers and cycads, which is indeed the probable position of these remarkable plants.
Grand d’Eury has divided the Cordaites into sub-genera, as follows:
1. Eucordaites.—Leaves spatulate, obovate, elliptical, or lanceolate, sessile, entire, with rounded apices and of leathery consistency. The leaves are from twenty to ninety centimetres in length. The nerves are either equally or unequally strong.
2. Dorycordaites.—Leaves lanceolate, with sharp points; nerves numerous, fine, and equal in strength. The leaves attain a length of from forty to fifty centimetres.
3. Poacordaites.—Leaves narrow, linear, entire, blunt at the point, with nerves nearly equally strong. The leaves are as much as forty centimetres in length.