178 THE EVOLUTION OF PLANTS 



had a peculiar habit, suggesting the Cabbage- 

 tree (Cordyline) of New Zealand or the Grass- 

 trees (Xanthorrhcea) of Australia. In all cases 

 the branching was of a forked nature, but the 

 two branches of the fork were often developed 

 unequally. 



The leaves were numerous, simple and grass- 

 like, attaining a great length (up to a yard) in 

 some species of Sigillaria. A very important 

 point is that every leaf had a ligule on its upper 

 surface, near the base, just as in the recent Sela- 

 ginellacese. The fructification was in the form 

 of well-defined cones, often of considerable size; 

 they were usually borne at the ends of the smaller 

 branches, but in Sigillaria were commonly pro- 

 duced on the main stems. 



The distinction between the two genera Lepi- 

 dodendron and Sigillaria depends, in the first 

 instance, on the arrangement of the leaf-bases, 

 which remained on the stem after the leaves 

 themselves had been shed, forming characteristic 

 patterns. The leaf-bases in Lepidodendron cover 

 more or less completely the surface of the stem, 

 and are commonly ranged in spiral or oblique 

 rows, while in Sigillaria the characteristic ar- 

 rangement is in vertical lines; in an important 

 section of the genus there are well-marked longi- 

 tudinal ribs, corresponding to the vertical series 

 of leaf-bases. Of the two, Lepidodendron appears 

 to have been the more ancient genus. 



