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CHAPTER LI. 



THE CARBONIFEROUS AND PERMIAN FLORAS. 



Carboniferous Plants. — The most extensive and the best 

 known of the Pah"eozoic Floras is that wliicli flourished dur- 

 ing the Carboniferous period. At this time were formed 

 those vast accumulations of vegetable matter which we know 

 as coal ; and much of our information as to the Carboni- 

 ferous plants is due to the value of coal, and to the vigour 

 with which coal-mining has been prosecuted. 



Coal consists of nearly pure carbon, with varying proportions of 

 hydrogen and oxygen and a small quantity of mineral matter. The 

 following are the conclusions arrived at by Dr Dawson as to the minute 

 structure of coal: 1. The so-called "mineral charcoal" or "mother 

 coal" consists chiefly of "bast-tissue" or of elongated cells derived from 

 the inner bark of Sigillarice and Lepidodendra . 2. Besides the above, 

 the mineral charcoal contains in many instances scalariform tissue 

 derived from Ferns, Sigillarice, Le2ndodendra, &c. 3. The coarse and 

 laminated portions of the coal are made up of vascular bundles, derived 

 apparently in the main from Ferns, along with other vegetable fragments, 

 and in some cases, though not to a great extent, the sporangia of some of 

 the Carboniferous Cryptogams. 4, In many parts of the coal occur dis- 

 cigerous or punctated woody fibres, belonging to Dadoxijlon, Sigillaria, 

 and Calamodendron. 5. A considerable portion of tlie coal is made up 

 of " epidermal tissue," which is " a dense cellular tissue representing the 

 outer integuments of various leaves, herbaceous stems, and fruits." 

 6. The layers of bright shining coal are composed of the flattened stems 

 and chiefly of the bark, of Sigillarice and other trees. 7. Some layers 

 of coal are occasionally composed mainly of the compressed leaves of 

 Gordaites. 8. Sporangia are often present in coal ; but they rarely 

 exist in such a proportion as to any extent actually to form the coal 

 tliemselves. In some of the English coals, however, the mass of the 



