THE CARBONIFEROUS PERIODS 



497 



female, the latter having a fleshy cover somewhat like a plum. Cor- 

 daites were on a level with the seed ferns as regards seeds, but in the 

 structure of the wood and in other respects they were more highly 

 organized. Cordaites became extinct before the close of the Paleozoic, 

 unless the ginkgo (p. 567) or maidenhair tree is a descendant. 



lift/ 





Fig. 476. — A, portion of trunk of a Catamites. The nodes and vertical stria- 

 tions are characteristic. Some grew to be sixty to ninety feet high. B, Annularia, 

 showing the characteristic arrangement of the leaves of the Calamites. 



True conifers possibly appeared before the close of the Paleozoic, 

 as the presence of the genus Walchia (Fig. 478) in the Permian 

 appears to show. 



Conditions under which the Coal Plants Grew. — The most abun- 

 dant plants of the Carboniferous swamps, the Calamites, Lepido- 

 dendron, and Sigillaria, had narrow leaves with a small surface ex- 

 posed to the sun. At the present time plants with leaves of this 

 character grow in the bright sunlight, while the leaves of shade plants 

 are large, the greater size being necessary in order that they may be 

 acted upon by a larger amount of light. Some of the coal plants, such 

 as the true ferns and seed ferns, had fairly large leaves, but they were 

 not of unusual size, indicating that they were only partially shaded by 

 the small-leaved Calamites and Sigillaria. From this evidence it 

 has been held that the Carboniferous plants did not live in a misty 

 atmosphere through which the sun's rays penetrated with difficulty, 

 but in one which was not unlike that of the present. 



