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A YEAR IN SCIENCE 



are known as pith, or medullary rays. The wood itself 

 is made of bundles of tubes known as vascular bundles. 

 Some of the tubes in each bundle are used for con- 

 ducting water from the root to the leaves, and others 

 for conducting prepared food materials downward. 



Cortex 



Vascular 

 Cylinder 



Pith 



Fibrovascular 

 Bundle 



Cambium 



Fig. 95. Cross section of a woody stem showing details of 

 structure. 



If a cross section of a young stem were examined 

 under a microscope, a region of thin-walled, rectangular- 

 shaped cells would be found between the wood and 

 bark regions. This is the growing region of the stem 



