THE CARBONIFEROUS PERIODS 



493 



observer, but a careful examination would show that instead of hav- 

 ing small sporangia on the back of the fronds they bore seeds, some- 

 times as large as hazelnuts, which were surrounded by a thick, fleshy 

 outer coat. The pteridosperm group 

 (Fig. 469) is interesting as a con- 

 necting type, since it is a link be- 

 tween the ferns, on the one hand, 

 and the cycads, which were the 

 dominant plants in the Mesozoic, 

 on the other. Whether it stands as 

 a connecting link between the ferns 



) 



Fig. 469. — Lyginodendron. Restora- 

 tion showing the stem, roots, and foliage; 

 a, seeds ; b, disks and pollen sacks. (After 

 Mrs. D. H. Scott.) 



T_. 470. — Restoration of Le'pidu- 

 dendron, showing the position and 

 character of the leaves, the fruit, and 

 the diamond-shaped markings on the 

 trunk. (See also Fig. 471.) Compare 

 the branching of Lepidodcndron with 

 that of Sigillaria. 



and the great groups of higher plants, or whether it leads to the cy- 

 cads and stops there, cannot as yet be affirmed. 



(3) Club Mosses (Lycopods). — The conspicuous trees of the 

 Carboniferous were gigantic club mosses, some of which grew to a 

 height of more than 100 feet. One of these, the Lepidodendron 

 (Greek, lepis, scale, and dendron, tree) was freely branched (Fig. 470) 



