174 



THE ANATOMY OF WOODY PLANTS 



any other lower seed plants in the present connection. The Gne- 

 tales and angiosperms present the next significant modification of 



structure in the 

 stem. Fig. 125 

 illustrates the 

 organization of the 

 axis of Ephedra 

 gerardiana. Obvi- 

 ously there are 

 numerous broad 

 bands of radial pa- 

 renchyma present. 

 Another feature of 

 interest is the pres- 

 ence of true vessels 

 in the cylinder of 

 secondary wood. 

 Broad rays of the 

 type found in 

 Ephedra and in the 



FIG. 126. Tangential section of wood of Ephedra 

 species, showing presence of large rays. 



angiosperms are 

 definitely corre- 

 lated with the ap- 

 pearance of vessels. 

 A tangential sec- 

 tion (Fig. 126) 

 through the wood 

 of Ephedra reveals 

 the true nature of 

 the rays in the 

 Gnetales. Fig. 127 

 illustrates the 

 organization of an 

 individual large ray 

 in the outer region 

 of the woody cylin- 

 der. The ray is 



FIG. 127. Portion of large ray highly magnified, 

 showing presence of tracheary elements in ray substance. 



