434 THE CARBONIFEROUS SYSTEM. 



Favularia has all the characters of the genus Clathraria. It is, 

 however, absolutely necessary to make some attempt at generic dis- 

 tinction among the diverse forms included in the genus Sigillaria ; 

 otherwise it will be impossible to reconcile the conflicting statements 

 of authors as to the dimensions, habit of growth, foliage, roots, and 

 fructification of these singular plants ; — such statements usually ap- 

 plying to one or more of the subordinate generic types. I shall 

 therefore notice separately, and with especial reference to their function 

 in the production of coal, the several generic or subgeneric forms, 

 beginning with that which I regard as the most important — namely, 

 Sigillaria proper, of which, in Nova Scotia, I regard the species which 

 I have named S. Brownii as the type. Other species are represented 

 in Figs. 161, B to K. 



In the restricted genus Sigillaria the ribs are strongly developed, 

 except at the base of the stem ; they are usually much broader than 

 the oval or elliptical tripunctate areoles, and are striated longitudinally. 

 The woody axis has both discigerous and scalarifonn tissues, arranged 

 in wedges, with medullary rays as in exogens ;* the pith is trans- 

 versely partitioned in the manner of Sternbergia ; and the inner bark 

 contains great quantities of long and apparently very durable fibres, 

 which I have, in my descriptions of the structures in the coal, named 

 " bast tissue." The outer bark was usually thick, of dense and almost 

 indestructible cellular tissue. The trunk when old lost its regular ribs 

 and scars, owing to expansion, and became furrowed like that of an old 

 exogenous tree. The roots were Stigmarim of the type of S. ficoides. 

 (Fig. 30, d, p. 180.) I have not seen the leaves or fruits attached; 

 but, from the association observed, I believe that the former were long, 

 narrow, rigid, and two-or- three-nerved (Cyperites), and that the latter 

 were Trigonocarpa, borne in racemes on the upper part of the stem. 

 These trees attained to a great size. I have seen one trunk four feet 

 in diameter, and specimens of two feet or more in diameter are com- 

 mon : some of these trunks have been traced for thirty or forty feet 

 without branching. The greater number of the erect stumps preserved 

 at the Joggins appear to belong to this genus, which also seems to 

 have contributed very largely to the formation of coal. Judging from 

 the paucity of their foliage, the density of their tissues, and the strong 

 structural resemblance of their stems and roots to those of Cycads, I 

 believe that their rate of growth must have been veiy slow. 



The genus Bhytidolepis, in which the areoles are large, hexagonal, 

 and tripunctate, and the ribs narrow and often transversely striate, 

 ranks as a coal-producer next to Sigillaria proper, and is equally 

 * Quart. Journ. Geol. Soc, paper on Structures of Coal. 



