Ch. xxvl] devonian period. 547 



botanical data obtained from Canada and the United States lead to 

 a similar conclusion respecting the flora of the same age in America. 

 Dr. Dawson, of Montreal, in an important memoir * on this subject, 

 after enumerating thirty-two genera of Devonian plants and sixty-nine 

 species collected in the State of New York and in Canada, observes 

 that they belong chiefly, as in the Carboniferous period, to Gymno- 

 sperms and Cryptogams. "When we peruse his catalogue of Conifer az. 

 Sigillarice, Catamites, Aster ophylUtes, Lepidodendra, Lepidostrobi, and 

 ferns of the genera Cyclopteris, JVeicropteris, Sphenopteris, &c, together 

 with fruits, such as Cardiocarpum and Trigonocarpum, we might well 

 suppose that we were presented with a list of carboniferous fossils ; 

 and, if told that the species differed, and that there was some admix- 

 ture even of genera unknown in Europe, we might be inclined to 

 ascribe such a want of agreement to geographical circumstances, and 

 especially to the distance of the New from the Old World. But 

 fortunately the coal formation is most fully developed on the other 

 side of the Atlantic, and is singularly like that of Europe, both litho- 

 logically and in a large proportion even of the species of its fossil 

 plants. There is also the most unequivocal evidence of relative age 

 afforded by superposition, for the Devonian strata in the United 

 States are seen to crop out from beneath the carboniferous on the 

 borders of Pennsylvania and New York, where both formations are of 

 great thickness. 



On comparing the species of the Middle Devonian in these coun- 

 tries with those of the Middle Coal-Measures, we find them all dis- 

 tinct, whereas some few species pass from the Upper Devonian into 

 the Lower Carboniferous rocks. The genus most characteristic of the 

 Devonian, and not found in the Coal, is one already alluded to, name- 

 ly, Psilophyton^ believed by Dr. Dawson to be a lycopodiaceous plant, 

 branching dichotomously (see P. princeps, fig. 618 A), with stems 

 springing from a rhizome, A b, which last has circular areoles, d e, much 

 resembling those of Stigmaria, and like it sending forth cylindrical root- 

 lets, such as at A c. The extreme points of some of the branchlets are 

 rolled up so as to resemble the croziers or circinate vernation of ferns, 

 h ; the leaves or bracts, i, supposed to belong to the same plant, are 

 described by Dawson as having enclosed the fructification. The re- 

 mains of Psilophyton princeps have been traced through all the mem- 

 bers of the Devonian series in Canada and the State of New York. 

 Some underclays in Gaspe are filled, as already stated, with its vertical 

 rootlets just as are the fire-clays of the coal, both in Europe and Ameri- 

 ca, with those of Stigmaria. 



One fragment of fossil wood, found some years ago by Professor 

 Hall, in a Devonian limestone of the Hamilton group, on Lake Erie, 

 has, according to Dawson,f the structure of an angiospermous exo- 



* Geol. Quart, Jouru., vol. xv. p. 477, 1859 ; also vol. xviii. p. 296, 1862. 

 f Ibid., vol. xviii. p. 305, 1862. 



