498 



HISTORICAL GEOLOGY 



L 



.->* 



Fig. 477. — Cordaites. Large trees 

 with long, narrow leaves sometimes 

 a yard in length. They are allied to 

 the conifers as well as to other orders 

 of plants. 



The character of the foliage of the 

 coal-making plants may, however, 

 have been an adaptation to con- 

 ditions which more than counterbal- 

 anced the effect of bright sunlight. 

 Their roots were those of water 

 plants, and their leaves were not 

 only narrow but were supplied with 

 various devices for preventing the 

 loss of water by rapid transpira- 

 tion. " If the water they grew 

 in had been fresh, they would 

 not have had such leaves, for 

 there would have been no need 

 for them to economize their water 

 (which is physiologically usable 

 in only small quantities in the 

 plant), but as we see in bogs and 

 brackish water to-day, plants only 



Fig. 478. — Stem and leaves of JValchia, a 

 characteristic Permian conifer. 



partly submerged protect their leaves from transpiring largely." 

 (Stopes.) 



The evidence at hand (p. 472) points to the existence of extensive 

 swamp areas which slowly sank as the half-decayed vegetation accu- 

 mulated on them, and which were so near sea level that a slight 

 sinking killed the vegetation growing there and buried them under 

 sand, clay, or lime ooze. It is probable, therefore, that the coal 

 plants (Catamites, Lepidodendron, Sigillaria) of the Carboniferous 

 lived not only in fresh but even grew out in the brackish water of 

 the shallow interior seas. 



