The latter author in 1891[61], in ignorance of Marion’s proposal to adopt the name _Gomphostrobus_, instituted a genus _Psilotiphyllum_ for the sporophylls of a species originally described by Geinitz[62] as _Sigillariostrobus bifidus_, but he subsequently adopted Marion’s designation and with some hesitation included the French and German specimens in the Psilotales. As stated elsewhere[63], Potonié’s arguments in favour of his view hardly carry conviction, and it is probably more in accordance with truth to deal with _Gomphostrobus_ in the chapter devoted to the Coniferales. _Psilophyton._ The generic title _Psilophyton_, instituted by the late Sir William Dawson[64], has become familiar to geologists as that of a Pre-Carboniferous plant characteristic of Devonian and Silurian rocks in Canada, the United States of America, and Europe. From the botanist’s point of view the name stands for miscellaneous remains of plants of different types and in many cases unworthy of record. The genus was founded on impressions of branched axes from the Devonian strata of New Brunswick resembling the rachis and portions of lateral pinnae of ferns or the forked slender twigs of a Lycopod. The type-species _Psilophyton princeps_ Daws. as represented on somewhat slender evidence in Dawson’s restoration, which accompanies the original description of the genus and has since been copied by several authors, is characterised by the possession of a horizontal rhizome bearing numerous rootlets and giving off dichotomously branched aerial shoots with spinous appendages, compared with rudimentary leaves, and terminating in slender branchlets bearing pendulous oval “spore-cases” from their tips. Some of the branchlets exhibit a fern-like vernation. The plant is spoken of by Dawson as apparently a generalised type[65], resembling in habit and in its rudimentary leaves the recent genus _Psilotum_ and presenting points of contact with ferns. Specimens were found in an imperfectly petrified state showing a central cylinder of scalariform tracheae surrounded by a broad cortical zone of parenchyma and fibrous tissue. Among other species described by the author of the genus we need only mention _Psilophyton robustius_, characterised by vegetative shoots and “spore-cases” similar to those of the type-species; but, as Solms-Laubach[66] has pointed out, the petrified sections referred by Dawson to _P. robustius_ are of an entirely different anatomical type from that of _P. princeps_[67]. British fossils from the Old Red Sandstone from the north of Scotland, Orkney and Caithness, originally figured by Hugh Miller and compared by him with algae but more especially with recent Lycopods, were subsequently placed by Carruthers[68] in the genus _Psilophyton_ as _P. Dechianum_, the specific designation being chosen on the ground that the Scotch specimens are specifically identical with fossils described by Goeppert[69] as _Haliserites Dechianus_.