THE STEM 



181 



long period considered them as belonging to the seed plants, since 

 all the types of the present age which possess marked secondary 

 growth are seed plants of gymnospermous or angiospermous affini- 

 ties. The situation in regard to the relation of sequence between 

 herbaceous and woody types might be almost endlessly illustrated, 

 but the examples cited will serve for the present. 



It has been assumed in the references to the large rays in the 

 alder and the oak 

 that , although 

 differing from one 

 another in organiza- 

 tion (in one case 

 aggregate and in the 

 other compound), 

 they have the same 

 morphological ex- 

 planation. It is 

 clear from the de- 

 scriptions supplied 

 in the present and a 

 foregoing chapter 

 that they are simi- 

 larly related to the 

 appendages. It is 

 now apposite to 

 establish the fact 



that the two types are related to one another in the particular 

 forms under discussion in the present connection. Fig. 134 illus- 

 trates the organization of the large ray in the wood of the root 

 of the red oak (Quercus rubrd) as seen in transverse section. It 

 is quite obvious that the structure differs from that found in 

 the stem as exemplified in Fig. 135 by the fact that the ray is 

 not homogeneous in its organization, but has numbers of fibers 

 intermingled with its parenchymatous elements. In other words, 

 the large mass of radial parenchyma under discussion must be 

 considered as being of aggregate organization and not as belong- 

 ing to the category of rays defined in an earlier chapter as 



FIG. 134. Transverse section of large ray in root of 

 Quercus r libra. 



