LEPIDODENDRON 



H5 



Lepidodendron selaginoides is at once distinguished 

 anatomically from the other species by the peculiar 

 structure of the central cylinder. No definite pith is 

 present ; the tracheae of the primary wood extend to 



Fig. 5g. — Lefiidodendron selaginoides. Transverse section of young branch, before 

 secondary wood has formed, jr, primary xylem-cylinder ; pc, zone of phloem and 

 pericycle ; c, inner cortex, differentiated into three layers ; c 2 , outer cortex ; pd, 

 periderm ; beyond this are the leaf-bases; Ig, ligule ; i.t, leaf-traces, at various points 

 on their outward course. X about 7. S. Coll. 1376. (G. T. G.) 



the centre of the stele (Figs. 59 and 60). The outer 

 part of the primary xylem has the structure usual in 

 the genus ; at the extreme periphery there are a 

 number of slightly prominent points, at and near which 

 the spiral elements are placed. Here then, as in other 



10 



