62 THE STRUCTURE OF ECONOMIC PLANTS 



There is great diversity and complexity among monocotyle- 

 donous stems in regard to tlie course of the bundles of the meristele. 

 In a large number of them, including the palms and some grasses, 

 the bundles conform to the plan which is briefly summarized below. 

 In these plants, the leaf base is very broad at its point of divergence 

 and commonly encloses the greater part of the stem or completely 

 encircles it at the node. Each leaf has a very large number of 

 bundles (it may exceed loo in Zea), and these enter the stem at 

 the node, extend downward through several successive internodes, 



Fig. 2.5. Transection of a sector of a stem of Zea showing the distribution of the bundles 



and mechanical tissues. 



and finally are united with the bundles of lower leaves. Because 

 of the regularity with which the bundles are anastomosed with 

 lower ones, and the uniformity of the distance that they extend 

 down the axis, approximately the same number of bundles may be 

 observed in transections at successive internodes. 



Some of the bundles extend down the outer periphery of the 

 vascular zone, while others lie nearer the center of the stem and 



