402 



VEGETATION OF THE CARBONIFEROUS PERIOD 



which this genus is often found is attributable partly to its charac- 

 teristic fructification being copiously produced, to its fronds being of a 

 hard texture and coriaceous consistence, and to the absence of hairs 

 or glands upon the under surface where the spores are produced, and to 

 the large size, smoothness, and evenness of the involucre, or organ pro- 

 tecting these spores. A few other ferns of this formation present the 

 fructification well preserved, and especially the genus Senftenbergia of 

 Corda* (Fig. 3, 1 & 2), which is allied to the recent Aneimidictyon 

 (Fig. 3, 3) ; but in no case except Pecopteris can the genus be thereby, 

 even provisionally, identified with any living one. 



The ferns are a group of plants, whose genera and species vary 

 extremely in the form of their fronds, and are sometimes so bizarre that 

 without the organs of fructification it is impossible to ascertain even on 

 the order they sometimes belong to. Now the fruit is so universally 

 present and abundant in recent ferns, that there is no difficulty in 

 defining the limits of the order as it now exists ; but in the case of fossil 

 ferns, in most species of which the fruit is of rare occurrence, and par- 

 tially obliterated by fossilization, it is impossible to decide whether 



* Corda "Flora der Vorwelt," Tab. 57, fig. 2. I have introduced a copy of Corda's 

 figure of the remarkable fructification of this plant ; as from the scarceness and high price 

 of that work it must be inaccessible to most of our readers. 



