THE CARBONIFEROUS AND PERMIAN FLORAS. 



493 



credits the assertion that discigerous tissue is present, and 

 describes the fruit as consisting of cones or strobiles. 



Leaving the botanical position of Sigillaria thus undecided, 

 we find that it is now almost universally conceded that the 

 fossils originally described under the name of Stigmaria are 

 the roots of Sigillaria, the actual connection between the two 

 having been in numerous instances demonstrated in an un- 

 mistakable manner. The Stigmaria (fig. 389) ordinarily pre- 

 sent themselves in the form of long, compressed or rounded 



Fig. 389. Stigmaria ficoides. Quarter natural size. Carboniferous. 



fragments, the external surface of which is covered with 

 rounded pits or shallow tubercles, each of which has a little 

 pit or depression in its centre. From each of these pits there 

 proceeds, in perfect examples, a long cylindrical rootlet ; but 

 in many cases these have altogether disappeared. In its 

 internal structure, Stigmaria exhibits a central pith surrounded 

 by a sheath of scalariform vessels, the whole enclosed in a 

 cellular envelope. The Stigmaria are generally found ramify- 

 ing in the " underclay," which forms the floor of a bed of coal, 

 and which represents the ancient soil upon which the Sigillaria 

 grew. 



Of the remaining genera of the Sigillarioids, Rhytidolepis is 

 the most important. It is characterised by the possession of 

 large, hexagonal, tripunctate areoles, and narrow, often trans- 

 versely striate ribs. In Favularia, lastly, the smaller branches 

 were destitute of ribs, with elliptical, spirally-disposed areoles. 

 The stem branched dichotomously like that of a Lepidoden- 

 dron and the leaves were broad, with numerous parallel veins, 

 approximating to the leaves of Cordaites. 



f. Conifera. True Conifers have long been known to occur 

 in the Carboniferous Rocks. They belong to the genera 

 Dadoxylon, Palceoxylon, Arancarioxylon, and Pinites. They 



