THE HISTORY OF PLANTS 



411 



(Figs. 26.11 and A. 18), so similar to true ferns that they cannot be dis- 

 tinguished by their foliage. Many other types of plants of unknown 

 relationships were also present. Some of the club mosses, horsetails, and 

 other plants grew to tree size and formed the first forests. One of the 

 best known of these forests was discovered at Gilboa in the Catskill 

 Mountains of New York, where petrified logs and many large upright 



Fig. 26.11. Restoration of a Carboniferous swamp forest in Illinois. The vertically ribbed 

 tree trunks are those of Sigillaria. The trunks with spirally arranged leaf scars and the twigs 

 with cones and grasslike leaves are Lepidodendron. Note the seed-fern fronds in center, some 

 bearing seeds at the tips. The small plants with whorled leaves are Sphenophyllum. (.Cour- 

 tesy Chicago Natural History Museum.) 



stumps were found. These trees were 40 feet tall, with crowns of slender 

 branches that bore three rows of small pointed leaves. They were long 

 thought to be seed bearers, but the supposed seeds have been found to 

 contain spores. 



The coal forests. The Devonian was followed by the Carboniferous 

 period, so named because it was the time when most of the important coal 

 deposits of the world were made. Vast swamps came into existence in 

 eastern North America, Europe, China, South Africa, and Brazil. The 



