XIIl] PSILOPHYTON 27 



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 rohuatius, characterised by 

 vegetative shoots and " spore-cases " similar to those of the type- 

 species ; but, as Solms-Laubach* has pointed out, the petrified 

 sections referred by Dawson to P. robustius are of an entirely 

 different anatomical type from that of P. princeps^. 



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 Carnithers' 

 in the genus Psilophyton as P. Dechianum, the specific designa- 

 tion being chosen on the ground that the Scotch specimens are 

 specifically identical with fossils described by Goeppert* as 

 Haliserites Dechianus. 



Various opinions have been expressed in regard to the 

 nature of the Devonian species Haliserites Bechianus Goepp. 

 with which Carruthers^ identified Miller's Old Red Sandstone 

 plant: reference may be made to a paper by White ^ containing 

 figures of dichotomously branched impressions described as 

 species of Thamnocladus which he includes among the algae. 



In describing some Belgian impressions of Devonian age as 

 Lepidodendron gaspianum Daws. Crepin'' states that Carruthers 

 has come to regard the specimens named by him Psilophyton 

 Dechianum as branches of a Lepidodendron; he also quotes 

 Carruthers as having expressed the opinion that the name 

 Psilophyton had been employed 'by Dawson for two kinds of 

 fossils, some being twigs of Lepidodendron while others, identi- 

 fied by Dawson as the reproductive branches of species 

 of Psilophyton, represent the spore-cases of ferns comparable 

 with Stur's genus Rhodea^. One of the examples figured by 

 Carruthers^ as P. Dechianum fi:om Thurso (preserved in the 

 British Museum, no. 52636), measuring 34 cm. in length and 



1 Solms-Laubach (95) A. ^ Dawson (71) A. Cf. PI. xi. figs. 131, 134, etc. 



' Carruthers (73). * Goeppert (52) A. » Carruthers (73). 



« White (02). ' Cr^pin (75). « Stur (75) A. p. 33. 

 » Carruthers (73). 



