140 MASS. EXPERIMENT STATION BULLETIN 170. 



slowly, the latter not growing more than 5 inches in diameter in seventy 

 years. 



To obtain the approximate growth of trees in any particular locality 

 would require measurements of a very large number of specimens. The 

 age of trees may be obtained by counting the annual rings of felled trees, 

 or by cores taken from the trunk of living trees, while the age of conifers 

 and others may be estimated by the number of internodes formed. There 

 is often a wide difference of opinion as regards the age of living trees, as 

 the total leaf area is seldom taken into consideration. Since trees acquire 



'0 20 50 40 50 60 70 80 90 100 110 120 iSOyrs 



KiG. 10. — Grand period of growth (cross-section measurements) of an elm 

 tree (Ulmus americana L.) in centimeters and decades. The maximum 

 growth occurred between the tenth and thirtieth years, followed by a 

 gradual decrease. From the nature of the curve we may conclude that 

 if the tree had survived under normal conditions it was capable of 

 developing for one hundred years more. 



practically all their structural material from the air by means of the 

 chemical processes going on in the leaves, it follows that those possessing 

 a large total leaf area grow much faster than those with a smaller leaf 

 area. A well-branched tree in the open will, therefore, grow six times as 

 fast as one in the forest under crowded conditions. Consequently there 

 is likely to occur much misconception regarding the age of living trees 

 on account of the marked variation in their rate of growth under different 

 conditions. The white pine, according to historical tradition, developed 

 feet in diameter and 250 feet in height in the New England primeval 

 forest, and elms as street trees are known to have lived two hundred years. 

 There are instances in Massachusetts where elms have lived to be 

 three hundred years old. Many shade trees live to be one hundred and 

 fifty years old and even more, and this age is not uncommon for forest 



