306 



HISTORICAL GEOLOGY. 



long, crowned with broad leaves, and with a spike of fruit. 

 It is probably a Cycad, or else a broad-leaved conifer like 

 the ginkgo. 



2. Ferns. These are the most abundant, but not the 

 largest, plants of the coal. About one half of all the 

 known species of coal-plants are ferns. They are often 

 beautifully preserved, large, complex fronds spread out 

 and pressed, as if between the leaves of a botanist's her- 

 barium, with even the microscopic veining of leaflets 

 visible. They are known to be ferns 1. By their large, 

 complex fonds (Fig. 231). 2. By the peculiar veining of 



FIG. 231. FIG. 232. FIG. 233. 



FIGS. 231-233. Coal -ferns: 231. Megaphyton, a coal-fern restored. (After Dawson.) 

 232. Callipteris Sullivanti. (After Lesquereux.) 233. Pecopteris Strongii. (After 

 Lesquereux.) 



the leaves, characteristic of ferns (Fig. 232). 3. By the 

 rows of spore-cases on the under surface of the leaves 

 (Fig. 234). 4. In the case of tree-ferns, by ragged, ovoid 

 marks, leaf-scars left by the fallen fronds. We give a few 

 figures of ferns of the American and French coal-measures. 

 The remaining orders, viz., Lycopods (or club-mosses) 

 and EquisetcB (horse-tails or scouring-rushes), are still 

 more important, for two reasons : 1. They formed the 

 principal mass of the coal. 2. They were very remarkable 

 examples of generalized types or connecting links, and 



