The Principles of Palaeontology. 205 



the distribution of species at the Carboniferous era is, so to say, 

 uaiversal. The same forms exist in the most widely separated 

 localities, where they appear and disappear simultaneously. 



The flora of Europe, of Siberia, of North and South America, 

 of. the Polar regions and of Tasmania present the closest analogy. 

 The greater part of the forms which compose this flora attain a 

 gigantic size ; these are the Lycopodiacea, Equisetacea, Ferns and 

 arborescent Cycads. The examination of this flora has led us 

 to conclude that the temperature at the Carboniferous epoch was 

 considerably elevated and uniformly distributed through all the 

 regions where the deposits of that age exist. But we no longer 

 hold to the hypothesis that that temperature was precisely torrid ; 

 neither is it necessary to suppose, as has been advanct-d, that the 

 atmosphere at that time was charged with vapor. An elevation 

 of some degrees suffices to explain the presence of arborescent 

 forms. The entirety of the characteristics of the coal flora, 

 which has its maximum of importance between 30° and 50° north 

 latitude, appears to indicate a maritime climate ; Europe and 

 North America must have been a sort of archipelago, in the 

 lagoons of which existed a warm and moist temperature. 



Several indications demonstrate moreover, that the preceding 

 data are not incompatible with the existence of climatic zones. 

 Still, the coal formations disappear south of 3u° of north 

 latitude, and we have no means of judging what transpired in the 

 Equatorial zone. Furthermore, there are some slight diversities 

 foand in the flora of the Arctic regions ; the Sigillarias are 

 wanting there. 



A new element of discussion has been brought forward by 

 "Waagen, who has discovered in the upper part of the Carbo- 

 niferous system almost indubitable traces of glacier action in 

 India, the Cape region, and southern Australia ; the flora of those 

 deposits, where are found rocks giving evidence of glacier trans- 

 portation, possesses characteristics which bring it into relation 

 with the flora of later periods. It is known, moreover, that 

 the presence of glaciers does not imply the existence of any 

 extreme cold ; elevated areas for condensation and great humidity 

 are sufficient. 



The uniformity of the coal flora is, moreover, a fact which 

 proves less than would that of plants of a higher organization. 

 The wide area of distribution of the Cryptogamia, both the 

 vascular and others, is indeed readily explained by the fact of the 

 lightness and abundance of their spores ; it is known also that 

 according to the law of the struggle for existence, localization is 

 much less pronounced in a flora of little variation than in a flora 

 of more varied forms, and that it is especially striking in types 

 of the highest organization. But the Dicotyledons and Mono- 

 cotyledons, which are the most perfect and most delicate plants, 

 and consequently the most restricted in locality, are wanting at 

 the epoch of which we speak. 



