150 THE ANATOMY OF WOODY PLANTS 



in question have no relation whatsoever to the pith, which in this 

 case is non-existent. On general evolutionary grounds there are 

 the best of reasons for regarding the type of organization present 

 in the root of the conifers and, in fact, of the gymnosperms in 

 general as more primitive than that which characterizes the stem, 

 and consequently of great value from the standpoint of the doctrine 

 of descent. 



FIG. 106. Root of Osmunda cinnamomea. Explanation in the text 



The root of the ferns and their allies differs from that found in 

 the gymnosperms only by the absence of secondary tissues. In 

 Fig. 106 is shown the root in Osmunda. Here central cylinder and 

 cortex are clearly delimited by the endodermis, composed of cells 

 with dark contents. Within this boundary lie the two masses of 

 phloem, and in the intervening region is seen the primary xylem. 

 This consists externally of narrow primitive elements which are 

 continued toward the center by the progressively broader tracheids 

 of the metaxylem. No secondary activities subsequently modify 



