43 2 



STUDIES IN FOSSIL BOTANY 



structure with normal secondary growth of the individual 

 stele. This is the great anatomical character of the 

 genus Medullosa, with its immediate allies, and separates 

 them at once from all plants now living, though there 



Fig. 165. — Merfullosa ang-lica. Part of transverse section, showing portions of two steles, 

 and leaf-traces going off from them, x, primary wood of steles ; x"-, secondary wood ; 

 ph, phloem ; It, leaf-trace, just detached from its stele ; i.ft, large leaf-trace, beginning 

 to divide. Other smaller bundles are shown, x 10. Phil. Trans., S. From a 

 photograph. S. Coll. 579. 



is one other fossil family (that of the Cladoxyleae) 

 which shares the peculiarity (see p. 496.) 



The secondary wood has the same structure as in 

 Heterangium or Lyginodendron (see Fig. 165). The 

 tracheides, which are in radial series, accompanied by 

 muriform medullary rays, are, as a rule, pitted on their 

 radial walls only The pits are multiseriate and 



