COAL PLANTS. 



489 



plants exhibit vegetable structure, are they mere impressions or are 

 they the plants themselves changed ? To what extent do these 

 agree with coal ? What particular plants and what parts of these 

 appear to have formed coal ? Its fibrous structure would hint at for- 

 mation from the woody system, and it is not incompatible with the 

 deliquescence of a thick layer of drift. 



The plants of coal fields having been drifted, can only give us an 

 idea of the vegetation along the natural drains of the then country, 

 such may by no means have had one universal character. 



The plants of the open surface of modern tropical countries being 

 generally different from those along the beds of streams, in which 

 situations now-a-days Equisetese, Lycopods and Filicis are chiefly 

 found. Coal being drift, it follows that the plants of the coal fields 

 can give us no information on the distribution of vegetables in those 

 days ; to gain information on this, the fossils should be in their origi- 

 nal situation. And there again an obstacle may exist in our not being 

 able to ascertain the height or level of that situation. 



If the plants of coal fields are found to be converted into coal, then 

 the only difference between coal shale, and coal will consist in the 

 very small proportion of vegetable matter in the former. 



The small number of coal plants, i. e. the small number of species, 

 at once points to the supposition that fossil plants are confined to 

 those of the most indestructible nature : here again is another sign of 

 this in the preponderance of Ferns, which Lindley finds to be the 

 most permanent. 



Hence the preponderance of Ferns, is by no means explainable by 

 their greatest simplicity of form, and consequent priority of formation. 



