THE ROOT 



149 



resin canals are found exclusively facing the clusters of protoxylem 

 and are never present in an axial position. 



In Fig. 105 an older 

 stage of the root of 

 Abies is presented. 

 Here the development 

 of the primary wood is 

 completed, and as a con- 

 sequence the axial resin 

 canal stands out more 

 distinctly. The second- 

 ary activity has pro- 

 ceeded so far that there 

 is now a considerable 

 zone of radially seriate 



xylem and phloem. The FIG. 104. Young root of Abies balsamea 



primary phloem has col- 



lapsed. The ap- 

 pearance of a layer 

 of cork or periderm 

 with radially dis- 

 posed elements is 

 obvious in the re- 

 gion of the endo- 

 dermis, and the 

 activity in this tis- 

 sue is the cause of 

 the death and the 

 ultimate shedding 

 of the external or 

 cortical region of 

 the root. It is 

 quite clear, as has, 

 indeed, been 

 pointed out above, 



that the radial parenchyma of the root of the conifers can in no wise 

 be appropriately designated medullary rays, since the structures 



FIG. 105. Photograph of an older root of Abies 

 balsamea. Description of this and foregoing figure in 

 the text. 



