THE STEM 



173 



however, that this is an inaccurate interpretation. The justice of 

 the criticism here advanced is, moreover, evidenced by reference 

 to the very conserva- 

 tive structures of the 

 root. Fig. 1 24 illus- 

 trates the central 

 region of this organ 

 in the same species 

 of spruce. The 

 primary xylem is 

 pronounced and dis- 

 tinctly centripetal in 

 the order of develop- 

 ment of its elements. 

 There is no medulla 

 present, and the rays 

 of the secondary 

 wood consequently 



FIG. 124. Root of Picea, showing primitive condition 



not only have no re- 

 lation to a medullary 

 region, but also end in the vicinity of the primary wood. It is 



clear that the radial 

 parenchyma of the 

 root cannot come 

 under the term 

 medullary ray, and it 

 will now be obvious to 

 the reader that in no 

 case can the radial 

 bands of storage tis- 

 sue in the secondary- 

 wood be accurately 

 called medullary rays. 

 They are properly de- 

 scribed as wood ravs. 

 It will not be 

 FIG. 125. Stem of Ephedra gerardiana necessary to consider 



