THE HERBACEOUS DICOTYLEDONS 



397 



tissues. It is clear in the radial view that there is in thin axes 

 no parenchyma subtending the leaf traces immediately below the 

 node. This situation necessitates the tangential aspect shown 

 below, where the leaf trace appears flanked by storage tissues 

 on either side. Plainly, therefore, by reason of the slenderness 

 of the woody cylinder and the great lengthening of the rays related 

 to the leaf traces, which may be regarded as in some measure a 



a b c d 



FIG. 274. Diagram of thicker and thinner axes of Vitis. Explanation in the 



text. 



compensation for their small radial dimension, axes of the vine 

 type approximate very closely those found in herbs. 



The discussion of typical herbs may now be advantageously 

 taken up; and it may here be remarked that, although necessary 

 brevity makes it impossible to consider more than a few instances 

 of the origin of the herbaceous stem, a wide investigation of the 

 situation in many groups of herbaceous dicotyledons has made 

 it clear that the same general conditions are present in every 

 instance. Fig. 275 reproduces part of a transverse section through 

 the upper slender region of the stem of the common stinging 



