THE CARBONIFEROUS AND PERMIAN FLORAS. 485 



CHAPTER XLV. 



THE CARBONIFEROUS AND PERMIAN FLORAS. 



CARBONIFEROUS PLANTS. The most extensive and the best 

 known of the Palaeozoic Floras is that which flourished during 

 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 Carboniferous 

 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 : 

 I. The so-called "mineral charcoal" or "mother coal" consists chiefly of 

 ' ' bast-tissue " or of elongated cells derived from the inner bark of Sigillaria; 

 and Lepidodendra. 2. Besides the above, the mineral charcoal contains in 

 many instances scalariform tissue derived from Ferns, Sigillari<z, Lepido- 

 dendra, &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 discigerous or punctated woody fibres, be- 

 longing to Dadoxylon, Sigillaria, and Calamodendron. 5- A considerable 

 portion of the coal is made up of "epidermal tissue," which is "a dense 

 cellular tissue representing the outer integuments of various leaves, herba- 

 ceous stems, and fruits." 6. The layers of bright shining coal are com- 

 posed of the flattened stems, and chiefly of the bark, of Sigillaria and 

 other trees. 7. Some layers of coal are occasionally composed mainly of 

 the compressed leaves of Cordaites. 8. Sporangia are often present in 

 coal ; but they rarely exist in such a proportion as to any extent actually to 

 form the coal themselves. 



As has been already observed, the types of plants which 

 are found in the Carboniferous Rocks are to a great extent 

 identical with those which composed the Devonian flora. 

 Specifically, however, the coal-plants are almost always distinct 

 from the Devonian forms. The number of plants already 

 known to have existed during the Carboniferous period is so 

 great, that nothing more can be done here than to draw the 

 attention of the student to some of the more important and 

 characteristic types. 



a. Filices. The Ferns of the Carboniferous period are 

 extremely numerous, and include both herbaceous forms like 

 the majority of existing species, and arborescent forms similar 

 to the living Tree-ferns of New Zealand. The latter belong 

 to the genera Psaronius, Caulopteris, and Palceopteris, of which 

 the two former occur in the older Devonian period. Of the 



