§ 33. FOSSIL PLANTS OF THE COAL. 713 



seems difficult to account for such an immense accumulation 

 of wood, and plants, and foliage, as would be required to 

 produce so enormous an amount of carbon, without any 

 intermixture of earthy detritus. Nor is it possible to con- 

 ceive that such beds could have been formed by the suc- 

 cessive submersion of a region covered with vegetation. 

 The shales above the coal are highly charged with carbon- 

 aceous matter, and contain a profusion of leaves and stems. 

 The vegetable remains are always in a carbonized state ; but 

 the leaves sometimes possess such a degree of tenacity and 

 elasticity as to be separable from the stone. The leaves 

 and seed-vessels which occur in the iron-stone nodules 

 have, in many instances, undergone a metallic impregnation, 

 as is often the case in specimens from Coalbrook Dale. 

 Brilliant sulphuret of iron, or pyrites, in some examples, 

 permeates the entire vegetable tissue; in others, the stems 

 and leaflets are replaced by white hydrate, or sulphate of 

 alumina ; and in many, by crystals of galena, or sulphuret 

 of lead, and of blende or sulphuret of zinc. In the sand- 

 stones, the stems have generally a carbonaceous crust, and 

 their internal structure is sometimes found in a calcareous, 

 and occasionally in a silicified state. 



The coal plants which have been accurately determined 

 amount to nearly a thousand species, of which two-thirds 

 are related to the ferns, and the higher tribes of the crypto- 

 gamia ; the remainder consist of coniferae, and a few flower- 

 ing monocotyledonous and dicotyledonous trees.* But 

 numerous species are undescribed, and new forms are 

 continually being discovered. 



* M. Adolphe Brongniart, in an interesting memoir on the genus 

 Noggerathia (Ann. des Sciences Naturelles, Janvier, 1846) states, that 

 according to the present state of fossil botany, the terrestrial vegetation 

 of the earth, at the carboniferous epoch, was limited to two of the grand 

 divisions of the vegetable kingdom, namely, "les Cryptogames aero- 

 genes oil Vasculaires, et les Phanerogames dicotyledones gymao- 

 spermes. , ' 



