3 6o 



THE ANATOMY OF WOODY PLANTS 



largely into its composition, and these are often in the condition 

 of septation. The ray, in fact, is a composite structure, organized 

 only partially from true radial parenchyma and also consisting 

 largely of transformed longitudinal fibrous elements of the wood. 

 These first become septate, and, particularly in the more external 

 regions of the wood, their divisions become progressively more and 

 more like the ordinary storage elements of the ray. Fig. 258 por- 

 trays the longitu- 

 dinal organization 

 of the wood in the 

 outer region of a 

 rather thick stem of 

 Ephedra calif or nica. 

 The large rays are 

 here conspicuous 

 and numerous, but 

 not of equal size. 

 In general, those of 

 greater dimensions 

 have originated in 

 the region of the 

 medulla, while 

 those less conspicu- 

 ous by their size 

 have come into ex- 

 istence more re- 

 cently. The small degree of magnification employed in the figure 

 does not make it possible to discern clearly the composite character 

 of the radial parenchyma. The next illustration, Fig. 129, which 

 reproduces one of the smaller radial masses under a higher magnifica- 

 tion, makes the organization of these structures apparent. Obvi- 

 ously not only ordinary radial parenchyma is concerned in the 

 constitution of the rays, but also numerous fibers and even vessels. 

 It may here be stated, although that situation is not clearly shown 

 in the illustration, that fibers are seen in such rays in all conditions 

 of transformation into elements resembling the ordinary radial 

 parenchyma. In the genus Ephedra we have the wedding, as 



FIG. 258. Tangential view of a large ray of Ephedra 

 in its external region. 



