
728 STRATIGRAPHICAL GEOLOGY. [Book VL 
believed by some botanists to be the cast of the pith of a woody “| 
stem belonging to some unknown tree, by others it is regarded as 
only a condition of the preservation of Calamites. : 
The Lycopods (Fig. 348) were represented by numerous species of _ 
the genus Lepidodendron, distinguished by the quincuncial leaf-scars 
on its dichotomous stem. Its branches, closely covered with pointed 
leaves, bore at their ends cones or spikes (Lepzdostrobus) consisting 
of a central axis round which were placed imbricated scales each 


B 
Fie, 347.—a, ANNULARIA SPHENOPHYLLOIDES (Zenker); B, ASTEROPHYLLITES. 
carrying a spore-case. Other conspicuous genera were Ulodendron, 
Knorria, Lepidophloios, Halonia, Cyclocladia. 
Among the most remarkable trees of the Carboniferous forests 
were the Sigillarioids, The genus Sigillaria was distinguished by the 
great height (fifty feet or more) of its trunk. Its stem was fluted, 
and marked by parallel perpendicular lines of leaf-scars, but as it 
grew, these external markings were lost (Fic. 349). The base of 
the stem passes into the roots known as Stigmaria, the pitted and 
tuberculed stems of which are such common fossils (Fig. 349, B, 
390), There can be little doubt, however, that Stigmaria was a 

