PLANT LIFE. 41 



of cells called cambium. It is this that is broken when 

 the bark is lifted in budding. The cambium is lack- 

 ing in palms and those other plants where there is no 

 distinction of cortex and woody portion. Sometimes 

 the wood is represented only by a few fibrous strands 

 arranged in a circle in the outer part of the pith next 

 to the cortex. These strands serve two purposes; 



\ 



SHOWING GROWTH OF TREES. 



they act as a skeleton to support the plant and as a 

 water conducting system, for it is through them that 

 the water ascends from the roots. In those plants 

 that live several years, such as trees and shrubs, these 

 fibrous strands increase in number and size, and the 

 spaces between become filled with wood fibers so that 

 all the space within the bark is a solid mass of wood. 

 This grows in thickness, by the layer of cambium next 

 to it turning to wood, while the cambium layer next 



