THE l'l.OKA OF THE COAL FORMATION. 



abundant in the Coal measures. These trees seem t<> have been of 

 smaller size and feebler structure than the last mentioned, and are 

 less frequently found in the erect position; but they arc very abun- 

 dant on the roofs of the coal beds. Judging from such specimens as 

 I have seen, their roots were less distinctly Stigmarioid than in the 

 last genus, though this appearance may arise from difference of pre- 

 servation. Their leaves were of the same type as in the last genus; 

 and their stems bear rings of irregular scars, which may mark stages 

 of growth, or the production of slender racemes of fruit in a vcrticillate 

 manner. The Avoody axis of the stems of this genus was composed 

 of scalariform and coarsely porous tissues, much like those of modern 

 Cycads. I figure, as an illustration of the genus, a fragment of S. 

 Bretonensis (Fig- 161, F). 



The genus Favularia is represented in Nova Scotia principally by 

 the typical species S. elegans of Brongniart. The admirable investi- 

 gations of the structure of the stem of this species by Brongniart, with 

 the further illustrations given by Corda, Hooker, and Goldenberg, 

 still afford the best general views of the structure of tiigillariai which 

 we possess. It is to be observed, however, that Brongniart's speci- 

 men was a young stem or a branch, and that it affords a very imper- 

 fect idea of the development of discigerous and bast tissues in the 

 full-grown stems of Sigillaria proper. The trees of this genus appear 

 to have been of small growth ; and they branched in the manner of 

 Lepidodendron, the smaller branches being quite destitute of ribs, and 

 with the areoles elliptical and spirally disposed. The stems show 

 joints or rings of peculiar scars at intervals, as in the last genus. The 

 leaves differ from those of the other genera, being broad and with 

 numerous slender parallel veins, almost in the manner of Cordahes 

 (Fig. 161, B 1 ). 



The genus Clathraria is evidently closely allied to the above, and 

 is possibly founded on branches of trees of the genus Favularia. It 

 is a rare form in Nova Scotia. 



Of the genus Leioderma or Asolanus I know but one species, inde- 

 pendently of those specimens of old trunks of the ordinary Sigillaria 

 in which the ribs have disappeared. My species, S. Sydeneruu, is 

 founded on specimens collected by Mr Brown at Sydney, (.'ape Breton, 

 which are especially remarkable for the curious modification which 

 thoy present of the Stigmarian root. The specimens described by Mi- 

 Brown under the name of S. alternans* and which have been copied by 

 Geinitz and Goldenberg, belong, I believe, to this species. 



* Quart. Journ. Geol. Soc, vol. v. p. 354. et seq. Bee also my paper on " Conditions 

 of Accumulation of Coal," Quart. Journ. Gcol. Soc, vol. xxii. p. 147, and PI. vii, 

 Figs. 28, a, 6, c. 



