220 WOODY BUNDLES. [BOOK i. 



interposed, while, on the contrary, in Endogens no such sepa- 

 ration occurs, and consequently the newly-formed matter of the 

 stem is forced towards the centre, through which it passes, 

 with a constant tendency, however, to reach the outside. I 

 confess, I do not perceive this analogy ; on the contrary, if 

 we compare the new shoot of an Asparagus and that of an 

 Elder-bush, the difference between them will be too great to 

 be thus explained away. M. Dutrochet thinks that in. the 

 globular rhizome of Tamus an argument may be found to 

 show the identity of Exogens and Endogens in the first period 

 of their growth ; but if this were admitted, it is equally evi- 

 dent, from the same example, that they become entirely dif- 

 ferent immediately after the first period. Nor, indeed, is 

 the anatomy of the woody tissue, which constitutes the 

 ligneous wedges of Exogens, the same as that which forms 

 the woody bundles of Endogens. In the latter each woody 

 bundle is, when divided transversely, described by Mohl as 

 consisting of the following parts (fig. 45.) : 



fig. 45. 



a Thick-sided woody tissue (cellules libri). 



b Bothrenchym (vasaporosa). 



c Thin-sided parenchym (vasa propria). 



e A variety of bothrenchymatous tissue (cellulce ligni punctate?). 



f Spiral vessels. 



But this is quite unlike the anatomy of the smaller portions 



