12 THE STORY OF PLANT LIFE 



vascular bundles forms primary medullary rays, 

 which carry water and nutrient solutes, not upward, 

 but laterally, and also store them up. 



By cambial activity similar types of secondary 

 tissues are formed, which serve the same sort of 

 function as in primary vascular bundles. Since it is 

 the object of the foregoing summary merely to 

 indicate the relative function of different tissues in 

 relation to the transport or storage of water or 

 food materials, or other functions, it is unnecessary 

 to describe the details of secondary vascular bundles 

 from the structural point of view. 



Nor has it been considered necessary to attempt 

 this in connection with the primary vascular 

 bundles, as this must come into a special study of 

 plant anatomy. 



So far cells and tissues have been considered. 

 They constitute the internal structure or body, if one 

 may so call it, of the plant. 



It is now necessary to briefly indicate the part 

 played by the organs of the plant, or the different 

 parts of which a plant is made up. 



In a general sense these are the root, stem, leaves, 

 flowers, fruit, and seeds. 



The function of the root itself is to retain the hold 

 of the plants upon the soil. This, in fact, is 

 almost the whole function of the roots of some 

 aquatic plants. For absorption takes place in their 

 case at all parts of the plant that are submerged, 

 and many aquatic plants float upon the surface, 



