PLANTS OF THE COAL. 



199 



them another genus termed caulopteris, which he considers 

 as true stems of tree-ferns. They are hollow ; but the mark^ 

 ings which they exhibit present so close a resemblance to 

 existing tree-ferns, as to render their identity with those 

 plants highly probable. They are, however, comparatively 

 rare, while of sigillaria, forty species have been discovered in 

 the coal. Figures of the fossil stem, caulopteris (fig. 134), 

 and of that of a familiar species of recent fern (fig. 135), are 

 placed in juxtaposition for comparison. 



FIG. 134. Caulopteris Phillipsii, 

 Lindley and Button. 



FIG. 135. Stem of recent tree-fern. 



II. LEPIDODENDBA. These are a very numerous class of 

 fossils from the coal. They have hitherto 

 been conjectured to be referable to the 

 family of club -mosses, and the larger 

 species were regarded as forming a tran- 

 sition to the coniferous plants. The living 

 species (fig. 136) of their supposed ana- 

 logues abound in tropical climates, they 

 generally creep on the ground, some grow 

 erect, but none exceed three feet in 

 height; whereas fossil specimens have 

 been found thirty feet high, while frag- 

 ments have been discovered indicating 

 a much larger size (fig. 137 and 138.)* 



FIG. 136. 



* See the references to the plates of this group, p. 189. 



