130 



MINUTE STRUCTURE OF THE STEM. 



classifications only one will be given here, and that only in part 

 and somewhat rearranged ; namely, de Bary's : 



I. The palm- type. A cross-sec- 

 tion of most monocotyledons shows 

 that the bundles are not arranged 

 in a simple ring, but that they are 

 irregularly scattered or more or 

 less crowded to form a shaft, which 



may be hollow as in most grasses, or filled in the centre with 

 parenchyma through which scattered bundles run. The periphery 

 of this cylinder or shaft is not a true bark, nor is the middle a 

 true pith. In the simple palm-type, all the bundles are leaf- 

 strands. 



II. The dicotyledonous type, in which all the primary bundles 

 are leaf- trace threads. The bundles are arranged in a simple 

 circle within which is pith, outside of which is cortex ; medullary 



FIG. 106. Transverse section through the outer part of the stem of Kunthia mon- 

 tana, a Palm. (Mohl.) 



FIG. 107. Transverse section through the middle part of the stem of Corypha 

 CCrifera, a Palm. (Mohl.) 



