46 CARBONIGENOUS ERA. 



been ascertained as entering into the composition of coal. 

 The ferns are plants which thrive best in warm, shaded, and 

 moist situations. In tropical countries, where these condi- 

 tions abound, there are many more species than in temperate 

 climes, and some of these are arborescent, or of a tree-like 

 size and luxuriance. ( 25 ) 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, existed in very high 

 latitudes. 



In the swamps and ditches of England there grows a plant 

 called the horse-tail, (cquisetum^) 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, reach- 

 ing the magnitudes of trees. While existing equiseta rarely 

 exceed three feet in height, and the stems are generally under 

 half an inch in diameter, their kindred, entombed in the coal 

 beds, seem to have been generally fourteen or fifteen feet 

 high, with stems from six inches to a foot in thickness. It is 

 to be remarked that plants of this kind (forming two genera, 

 the most abundant of which is the calamites) are only 

 represented on the present surface by plants of the same 

 family : the species which flourished at this era gradually 

 lessen in number as we advance upwards in the series of rocks, 

 and disappear before we arrive at the tertiary formation. 



The club-moss family (lycopodiacece) are other plants of the 

 present surface, usually seen in a lowly and creeping form in 

 temperate latitudes, but presenting species which rise to a 

 greater magnitude within the tropics. Many specimens of 

 this family are found in the coal beds ; it is thought they 

 have contributed more to the substance of the coal than any 

 other family. But, like the ferns and equisetaceae, they rise 

 to a prodigious magnitude. The lepidodrendon (so the fossil 

 genus is called, from the scaly exterior) has probably been 

 from sixty-five to eighty feet in height, having at the base a 



