TOO M. De Canclolle on Fossil Vegetables. 



fresh-water or a salt-water plant, requiring a dry or a moist si- 

 tuation, a very warm or a merely temperate climate. We easily 

 judge of these circumstances by the conditions which are neces- 

 sary to plants of analogous forms, which exist at tlie present 

 time. 



M. Brongniart has supplied us with many of these indications 

 with remarkable sagacity. 



The arborescent astheogamea- of the first period, must have 

 lived in an atmosphere which was hotter and more humid than 

 that of islands now situated immediately under the equator. 

 We know that the ferns and lycopodcJB of temperate and nor- 

 thern climates are always little plants, with a creeping stem, 

 which frequently hides itself in the earth. Towards the equa- 

 tor, tree-ferns and lycopodiaceas are found. Their number is the 

 greater as the region is hotter and more moist. M. Brongniart 

 has concluded, and apparently with reason, that the forests 

 which formed the coals must liave probably existed upon 

 islands, and at a time when the temperature of the globe was 

 higher than at present. The islands of Ascension and St He- 

 lena, where the ferns and analogous plants form about a third, 

 or even the half, of the number of phanerogamous plants, ap- 

 proach somewhat to this antique vegetation, only the sizes of the 

 species are far more diminutive. 



The islands or archipelagoes which have formed the basins 

 for the coal, were surrounded by an ocean, of which the transi- 

 tion series is the index. 



Some geologists have thought that the fossil trees of coal 

 mines have been transplanted thither from the neighbouring 

 lands ; and they have endeavoured to support this opinion, in- 

 asmuch as there are examples of the vertical position of trunks 

 of trees which have been thus transported : but this hypothesis 

 is quite rejected by other naturalists. M. Brongniart supports, 

 quite to demonstration, the opinion of De Luc, that the trees of 

 coal-mines have been covered over in situ ; and Messrs Hutton 

 and Lindley, who have recently discussed the question *, are of 

 the same opinion. 



In explaining the carbonized nature of coal, M. Brongniart 



• Introduction to second volume of Fossil Flora. 



