462 



PENNSYLVANIAN PERIOD 



The trunks of some lepidodendrons were 100 feet in length. 

 They were erect, and branched at a great height. The leaves were 

 linear or needle-shaped, ranging up to six or seven inches in length, 

 and set densely on the branches. Some of them had characteristics 



Fig. 398. Leaf markings 

 of a lepidodendron. 



Fig. 399- 

 sigillarian. 



Leaf markings of a 



pointing in the direction of seeds, but it is not known that seed- 

 producing plants sprang from them. More than 100 species of 

 lepidodendrons have been described. They seem to have reached 

 their climax early in the period, and nearly all had disappeared by 

 its close. 



The sigillarians differed from the lepidodendrons in being with- 

 out many branches. They were perhaps the largest of the trees, 

 their trunks reaching six feet in diameter, and 100 feet or more in 

 height. The stems were densely clothed with erect, rigid, linear 

 leaves. They were more abundant than lepidodendrons before the 

 close of the period, but were on the wane at its close. 



The group is essentially Pennsylvanian but initial forms lived 

 in the Devonian and Lower Carboniferous, and a few survived to 

 the Permian. 



Cordaitales. One of the characteristic trees of the period was 

 Cordaites, which belonged to a remarkable family (now extinct) of 

 gymnosperms. The trees were 90 feet or more in height, and rather 

 slender. The wood was of the coniferous type, covered, as in so 

 many other plants of the period, by a thick bark. The trunks had 

 a large pith. The leaves were parallel veined, suggestive of mono- 

 cotyls of the yucca type, and in some cases attained a length of six 



