SELA GIN ELL A CE^ 



43 



trie and closed. In the centre is the xylem, consisting chiefly of scalari- 

 form and reticulate tracheides ; this is completely surrounded by the 



FIG. 23. Transverse section through leaf of 6". in&qualifolia. ch, chlorophyll-bodies ; co, 

 upper epiderm ; eu, lower epiderm ; sp, stomates ; /, air-cavity surrounding vascular bundle 

 and traversed by trabecules. (After Goebel, magnified.) 



FIG. 24. Transverse section of stem of 6". denticulata Lk. b, air-cavity 

 surrounding ' vascular ' bundle. (After Goebel, magnified.) 



thin- walled phloem. The primary elements of the xylem, very narrow 

 spiral tracheides, are formed at the angles of the bundle, and from them 



