LAND PLANTS AND ANIMALS. 



tained as entering into the composition of coal. The ferns are 

 plants which thrive best in warm, shaded, and moist situations. 



FIG. 26. 



Pecopteris aquilina. 



In tropical countries, where these conditions abound, there are 

 many more species than in temperate climes, and some of these 

 are arborescent, or of a tree-like size and luxuriance. The 

 ferns of the coal strata have been of this magnitude, and that 

 without regard to the regions of the earth where they are found. 

 In the coal of Baffin's Bay, of Newcastle, and of the torrid 

 zone, alike, are the fossil ferns arborescent, showing that in that 

 era, the present tropical temperature, or one even higher, ex- 

 isted in very high latitudes. 



In the swamps and ditches of England there grows a plant 

 called the horse-tail, (equisetum,) having a succulent, erect, 

 jointed stem, with slender leaves, and a scaly catkin at the 

 top. A second large section of the plants of the carboniferous 

 era were of this kind, (equisetacece,) but, like the ferns, reaching 

 the magnitude of trees. While existing equiseta rarely exceed 



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