130 



THE GEOLOGICAL HISTORY OF PLANTS. 



species of ArchcBopteris, of the Upper and Middle Brian, 

 are eminent as examples. This type, howeyer, scarcely 

 extends as high as the coal-formation.* Some of the 

 tree-ferns of the Carboniferous present yery remarkable 

 features. Oue of these, of the genus Megaphyton, seems 

 to have two rows of great leayes, one at each side of the 

 stem, which was probably sustained by large bundles of 

 aerial roots (Fig. 56). 



In the Carboniferous, as in the Erian, there are leaves 

 which have been referred to ferns, but are subject to 

 doubt, as possibly belonging to broad-leaved taxine trees 

 allied to the gingko-tree of China. One of these, repre- 

 sented in Fig. 57, has been 

 found in the coal-formation of 

 Sfova Scotia, and referred to the 

 doubtful genus Noeggerathia. 

 Fontaine has proposed for simi- 

 lar leaves found in Virginia the 

 new generic name Saportea. 



Ferns, as might be inferred 

 from their great age, are at the 

 present time dispersed over the 

 whole world ; but their head- 

 quarters, and the regions to 

 which tree-ferns are confined, 

 are the more moist climates of the tropics and of the 

 southern hemisphere. The coal-swamps of the northern 

 hemisphere seem to have excelled even these favoured 

 regions of the present world as a paradise for ferns. 



I have already stated that the Carboniferous consti- 

 tutes the headquarters of the Cordaites (Fig. 58), of which 

 a large number of sjDecies have been described, both in 



Fig. 57. — Noeggerathia dispar 

 (half natural size). 



* The pretty little ferns of the genus Sotrychium (moonwort), so 

 common In American and European woods, seem to be their nearest mod- 

 em allies. 



