FOSSIL FERNS. 



717 



specimens before us (Lign. 157, 158). The fructification 

 on the back of the leaf is sometimes preserved. 



The stems, with their elliptical cicatrices, or scars, bear 

 some resemblance to those of the palms, but are readily 

 distinguished, from their longest diameter being vertical, 

 while in the palms it is transverse : sections of the stems 

 of these two tribes have also distinctive characters.* The 



1. 



Lign. 158.— From Coalbrook Dale. 

 Fig. 1 . Asterophyllites Parkinsoni. 

 — 2. Pecopteris Mantelli. 



large tree-ferns are confined almost exclusively within the 

 tropics; humidity and heat being the conditions most 

 favourable to their develop- 

 ment. In the coal, there are 

 not less than 150 species of 

 ferns, nearly all of which be- 

 long to the tribe of Polypodia- 

 cece; the common Polypody, 

 so frequent on old walls, will 

 convey an idea of the charac- 

 ters of their foliage. The 

 fossil species present great Lign1 

 variety and elegance in the from coalbrook Dale. 



* Y6getaux Fossiles, torn. i. pi. 37. 



