The earlier writers regarded the pith-casts as stems with scars of amplexicaul leaves: Artis[640] described specimens from the English Coal Measures as _Sternbergia_, one of which he stated to be 6 ft long; a few years later Sternberg[641] proposed the name _Artisia_ and this has been generally used on the ground that _Sternbergia_ is the name of a recent flowering plant. A specimen of _Artisia transversa_ (Art.) from the Coal Measures of Yorkshire is shown in fig. 466, B, and similar specimens varying considerably in diameter up to about 10 cm. are abundant in European and American Coal Measures. The prominence and depth of the transverse ridges, the presence or absence of anastomoses between adjacent discs are, as Zeiller[642] says, of very doubtful value as specific characters. Dawson in 1846[643] spoke of _Artisia_ as probably the pith of a tree, a view suggested to him by Mr Dawes. In 1851 Williamson[644] published a description of some specimens in which a pith-cast, _Artisia approximata_ Lind. and Hutt., was enclosed by wood showing very clearly Cordaitean characters. Further demonstration of the true nature of _Artisia_ was supplied by Grand’Eury from St Étienne material. If the generic name _Artisia_ is applied to all pith-casts showing the transverse ridges and grooves like those seen in fig. 466, B, it must be remembered that it is not safe to assume a connexion with _Cordaites_ or _Mesoxylon_. A Liassic species described by Lignier[645] from France as _Artisia alternans_ is quoted by authors as evidence of the persistence of _Cordaites_ into the Jurassic period; but in view of the fact that the discoid type of pith is not by any means confined to _Cordaites_ or even to the Cordaitales the occurrence of _Artisia_ is in itself of no great botanical significance. It is also true that a discoid pith is not an invariable attribute of stems closely allied to the genus _Cordaites_; but if these reservations are made the use of the generic term _Artisia_ serves a useful purpose. ii. _Petrified stems._ =Dadoxylon.= Endlicher.