LAND PLANTS AND ANIMALS. 51 



gious magnitude. The lepidodendron (so the fossil genus is 

 called, from the scaly exterior) has probably been from sixty- 

 five to eighty feet in height, having at the base a diameter of 

 about three feet, while the leaves measured twenty inches in 

 length. In the forests of the coal era, the lepidodendra would 

 enjoy the rank of firs in our forests, affording shade to the 

 only less stately ferns and calamites. The internal structure 

 of the stem, and the character of the seed-vessels, show them 

 to have been a link between single-lobed and double-lobed 

 plants a fact worthy of note, as it favours the idea of a pro- 

 gress in vegetable creation, in the line of an improved organiza- 

 tion. It is also curious to find a missing link of so much 

 importance in a genus of plants which has long ceased to have 

 a living place upon earth. 



The other leading plants of the coal era are without repre- 

 sentatives on the present surface, and their characters are in 

 general less clearly ascertained. Amongst the most remark- 

 able is the sigillaria, of which large stems are very abundant, 



FIG. 29. 



Sigillaria undulata. 



showing that the interior has been soft, and the exterior fluted, 

 with separate leaves inserted in vertical rows along the flutings. 

 Masses to which the term stigmaria is applied, were originally 

 described as distinct plants, but are now generally regarded as. 

 fragments of the root and stem of Sigillarise. Amongst mono- 

 cotyledons were some palms, (flabeUaria and noeggeraihia,} be- 

 sides a few not distinctly assignable to any class. 



The true conifers of the coal are comparatively rare, and are 

 only as yet found in isolated cases, and in sandstone beds. 



E 2 



