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appear that the stem of a perennial plant would have unlimited growth 

 in length. The vascular cambium of woody stems also is perennial, with 

 alternating periods of growth and dormancy. Trees and shrubs, therefore, 

 might be expected to increase in diameter indefinitely. 



From observation, however, it is evident that there are limits to the 

 age of trees and also to both height and diameter growth of stems. Fur- 

 thei-more, among the different species there is a wide range in these 

 limits. The smallest species of trees never exceed a few feet in height 

 and a few inches in diameter. Among herbaceous plants there are 

 many species that are even more restricted in age, height, and diameter. 

 The tallest trees may exceed 300 feet, and the diameter of some trees 

 may become more than 30 feet. Vines in the tropics may become a thou- 

 sand feet or more in length. 



Fig. 101. A giant sycamore 45 feet in circumference at breast height. White River 

 Valley, Indiana. Photo by G. W. Blaydes. 



