470 



FERNS— LEPIDODENDRON. 



[Ch. XXIV 



been referred to this genus. They consist of cylindrical stems or 

 trunks, covered with leaf-scars. In their mode of branching, they 

 are always dichotomous (see fig. 518). They are considered by 

 Brongniart and Hooker to belong to the Lycopodiacece, plants of this 

 family bearing cones, with similar sporangia and spores (fig. 521). 

 Most of them grew to the size of large trees. The figs. 517-519 



Tig. 517. 



Fig. 518. 



Lepidodendron Sternoergii. Coal-measures, near Newcastle. 

 Fig. 517. Branching trunk, 49 feet long, supposed to have belonged to L. Sterribergii. 



(Foss. Flo., 203.) 

 Fig. 518. Branching stem with bark and leaves of L. Stembergii. (Foss. Flo., 4.) 

 Fig. 519. Portion of same nearer the root ; natural size. (Ibid.) 



represent a fossil Lepidodendron, 49 feet long, found in Jarrow Col- 

 liery, near Newcastle, lying in shale parallel to the planes of stratifica- 

 tion. Fragments of others, found in the same shale, indicate, by the 

 size of the rhomboidal scars which cover them, a still greater magni- 

 tude. The living club-mosses, of which there are about 200 species, 

 are most abundant in tropical climates. They usually creep on the 

 ground, but some stand erect, as the Lycopodium densum from New 

 Zealand (fig. 520), which attains a height of 3 feet. 



Fig. 520. 



a. Lycopodiwm demum ; banks of E. Thames, New Zealand. 



b. Branch, natural size. c. Part of same, magnified. 



