26 PSILOTALES [CH. 



The latter author in 1891 ^ in ignorance of Marion's proposal to 

 adopt the name Oomphostrobus, instituted a genus Psiloti- 

 phyllum for the sporophylls of a species originally described by 

 Geinitz^ 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 ^ Potonie's arguments in favour of his view hardly 

 carry conviction, and it is probably more^in accordance with 

 truth to deal with Oomphostrobus in the chapter devoted to 

 the Coniferales. 



Psilophyton. 



The generic title Psilophyton, instituted by the late Sir 

 William Dawson*, 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 princepe 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®, re- 

 sembling in habit and in its rudimentary leaves the recent 

 genus Psilotum and presenting points of contact with ferns. 



1 Potoni6 (91); (93) A. p. 197. 



2 Geinitz (73) p. 700, PL iii. figs. 5—7. 



3 Seward and Gowan (00) p. 137 ; Seward and Ford (06) p. 874. 

 * Dawson (59) A. p. 478, fig. 1. s jjj^j (71) ^ p 33 



