86 



PICTURESQUE SKETCHES 



singular club-mosses (ycopodiace<e), so close as al- 

 most to justify the opinion of its having formed a 

 connecting link between these two very different natu- 

 ral tribes of plants. 



Another genus, the iSigillaria* (fig. 31), must, if 

 recent observations are correct, be considered as the 

 stem of the tree of which the so-called Stigmaria-^ 

 was only the root. It was even more abundant, and 

 a still more important element in the formation of 

 coal, than the Lepidodendron. The stems of Sigilla- 

 rise exhibit no internal woody structure, having been 



SIGILLARIA. Trunk and Roots. 



for the most part either hollow or succulent, and easily 

 crushed, but they were evidently provided with a cen- 

 tral woody axis, and also with an outer coating of bark, 

 the latter often turned into coal, and sometimes be- 

 ing nearly an inch in thickness. The whole of the 

 trunk is elegantly fluted, and there is a single row of 

 small scars, the remains of leaves, at regular distances 



* From the Latin sigillum, a seal, or the impression made by it ; the 

 trunk of the tree appearing to have been stamped with a pattern in regu- 

 lar rows along the direction of its length. 



t Srty/ia (stigma), a mark. The fossil was called Stigmaria, from the 

 regular and deep marks or brands impressed on the supposed stem or root. 



