346 CALAMITES. 



that are preserved in the Strata of the Carboniferous Order, 

 beginning with those which are common both to the ancient 

 and existing states of Vegetable Life. 



Equisetacece.* 



Among existing vegetables, the Equisetacese are well 

 known in this chmate in the common Horse-tail of our 

 swamps and ditches. The extent of this family reaches 

 from Lapland to the Torrid Zone, its species are most 

 abundant in the temperate zone, decrease in size and num- 

 ber as we approach the regions of cold, and arrive at their 

 greatest magnitude in the warm and humid regions of the 

 Tropics, where their numbers are few. 



M. Ad. Brongniartf has divided fossil Equisetacese into 

 two Genera ; the one exhibits the characters of living 

 Equiseta, and is of rare occurrence in a fossil state ; the 

 other is very abundant, and presents forms that differ mate- 

 rially from them, and often attain a size unknown among 

 living Equisetacese ; these have been arranged under the 

 distinct genus Calamites,'^ they abound universally in the 

 most ancient Coal formation, occur but sparingly in the 

 lower strata of the Secondary series, and are entirely want- 

 ing in the Tertiary formations, and also on the actual sur- 

 face of the earth. 



The same increased development of size, which in recent 



* See PI. 1. Fig. 2. 



t Histoiredes Vegetaux Fossils, 2d Livraison. 



t Calamites are characterized by large and simple cylindrical stems, articu- 

 lated at intervals, but either without sheaths, or presenting them under forms 

 unknown among existing Equiseta ; they have sometimes marks of verti- 

 cillated Branches around their articulations, the leaves also are without 

 joints. But the most obvious feature wherein they differ from Equiseta, is 

 their bulk and height, sometimes exceeding six or seven inches in diameter, 

 whilst the diameter of a living Equisetum rarely exceeds half an inch. A 

 Calamite fourteen inches in diameter has lately been placed in the Museum 

 at Leeds. 



