THE CARBONIFEROUS PERIOD. 167 



these spore-cases ; whilst inferior kinds possess a progressively 

 increasing amount of the dull carbonaceous substance which is 

 known as " mineral charcoal, " and which is undoubtedly com- 

 posed of "the stems and leaves of plants reduced to little 

 more than their carbon. " On the other hand, Principal Daw- 

 son finds that the American coals only occasionally exhibit 

 spore-cases to any extent, but consist principally of the cells, 

 vessels, and fibres of the bark, integumentary coverings, and 

 woody portions of the Carboniferous plants. 



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 notice briefly the typical and characteristic 

 groups of these such as the Ferns, the Calamites, the Lepido- 

 dendroids, the Sigillarioids, and the Conifers. 



In accordance with M. Brongniart's generalization, that 

 the Palaeozoic period is, botanically speaking, the " Age of 

 Acrogens, " we find the Carboniferous plants to be still mainly 

 referable to the Flowerless or " Cryptogamous " division of the 

 vegetable kingdom. The flowering or " Phanerogamous " 

 plants, which form the bulk of our existing vegetation, are hardly 

 known, with certainty, to have existed at all in the Carbon- 

 iferous era, except as represented by trees related to the existing 

 Pines and Firs, and possibly by the Cycads or " false palms. "* 

 Amongst the " Cryptogams, " there is no more striking or 

 beautiful group of Carboniferous plants than the Ferns. Re- 

 mains of these are found all through the Carboniferous, but in 

 exceptional numbers in the Coal-measures, and include both 

 herbaceous forms like the majority of existing species, and 

 arborescent forms resembling the living Tree-ferns of New 

 Zealand. Amongst the latter, together with some new types, 

 are examples of the genera Psaronius and Caulopteris, both of 

 which date from the Devonian. The simply herbaceous ferns 

 are extremely numerous, and belong to such widely-distributed 

 and largely-represented genera as Neuropteris, Odontopteris (fig. 

 108), Alethopteris, Pecopteris, Sphenopteris, Hymenophyllites, &c. 



The fossils known as Calamites (fig. 109) are very common 

 in the Carboniferous deposits, and have given occasion to an 

 abundance of research and speculation. They present them- 

 selves as prostrate and flattened striated stems, or as similar 



* Whilst the vegetation of the Coal-period was mainly a terrestrial one, 

 aquatic plants are not unknown. Sea-weeds (such as the Spirophyton 

 cauda-Galli) are common in some of the marine strata ; whilst coal, accord- 

 ing to the researches of the Abbe Castracane, is asserted commonly to 

 contain the siliceous envelope of Diatoms. 



