STRUCTURE AND REQUIREMENTS OF TREES 111 



of moisture. Botanists have taken the moisture factor 

 as the basis of classification and have subdivided trees 



FIG. 89. Dead Branches at the Top Caused by Insufficient Water. 



into those that grow in moist places (hydrophytes), those 

 that grow in medium soils (mesophytes) , and those that 

 grow in dry places (xerophytes) . Water is taken up by the 



