Woody | Medullary rays | Generic | Geological fibres. | and pith. | names. | age. -------------+--------------------+---------------------+--------------- No discs. | One or two series | _Aporoxylon_, | Devonian | of cells. | Unger. | (Erian). -------------+--------------------+---------------------+--------------- | Complex, or of two | { _Pitus_, | | or more series of | { Witham. | Middle and | or more series of | { _Palæoxylon_, | Lower | cells. | { Brongniart. | Carboniferous | Pith Sternbergian. | { _Pissadendron_, | and Devonian. | | { Endlicher. | +--------------------+---------------------+--------------- Discs in one | Simple, or of one | { _Araucarites_, | series | row of cells. | { Goeppert | Upper contiguous, | Pith Sternbergian. | { _Dadoxylon_, | Carboniferous or in | | { Endlicher. | and Permian. several | | { _Araucarioxylon_, | series | | { Schimper. | spirally +--------------------+---------------------+--------------- arranged. | Pith in spherical | _Ormoxylon_,[CQ] Dn. | Devonian. | chambers. | | +--------------------+---------------------+--------------- | Medullary sheath | | Devonian. | scalariform. | _Dadoxylon_ | | Medullary rays | (Cordæoxylon),[CR] | | frequent, simple, | Dn. | | short. | | -------------+--------------------+---------------------+--------------- [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.