COMMENCEMEjy OF LAND PLANTS. 41 



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--noss family (k copodiacece) are other plants 

 of the present surface, usually seen in a lowly and creep- 

 ing 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 

 lepidodendra (so the fossil genus is called) have probably 

 beer! from sixty-five to eighty feet in height, having at 

 their base a diameter of about three feet, while their 

 leaves measured twenty inches in length. In the forests 

 of the coal era, the lepidodendra would enj oy the rank of 

 firs in our forests, affording shade to the only less stately 

 ferns and calamites. The internal structure of the stem, 

 and the character of the seed-vessels, show them to have 

 been a link between single-lobed and double-lobed plants, 

 a fact worthy of note, as it favors the idea that, in vegeta- 

 ble as well as animal creation, a progress has been ob- 

 served, in conformity with advancing conditions. It is 

 also curious to find a missing link of so much importance 

 in a genus of plants which has long ceased to have a liv 

 ing place upon earth. 



The other leading plants of the coal era are withouf 

 representatives on the present surface, and their charac- 

 ters are in general less clearly ascertained. Amongst the 

 most remarkable are — the sigillaria, of which large sterna 

 are very abundant, showing that the interior has been 

 soft, and the exterior fluted with separate leaves inserted 

 in vertical rows along the flutings — and the stigmaria 

 plants apparently calculated to flourish in marshes 01 

 pools, having a short, thick, fleshy stem, with a dome- 

 shaped top, from which sprung branches of from twenty 

 to thirty feet long. Amongst monocotyledons were some 

 palms, (flabellaria and nceggerathia,) besides a few not 

 distinctly assignable to any class. 



The dicotyledons of the coal are comparatively few ; 

 though on the present surface they are the most numerous 

 sub-class. Besides some of doubtful affinity {annularia. 

 asterophyllites, &c.) there were a few of the pine family, 

 tvhich seem to have been the highest class, of trees o 



