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NEBRASKA STATE HORTICIILTURAL SOCIETY. 



The table shows that all the species except silver maple make a better 

 height growth during the first five years than for any other five-year 

 period. Silver maple increases its rate of height growth over that of 

 the first five years up to the twentieth year, and thereafter slowly de- 

 clines. Cottonwood, green ash, and black walnut decline in height growth 

 after the thirtieth year, the first two very rapidly. Black walnut main- 

 tains a very uniform growth up to that time. Hardy catalpa grows at 

 a fairly uniform rate up to the twentieth year, and then gradually 

 declines. Honey locust grows somewhat more slowly than hardy catalpa 

 for the first ten years, but leads after that tme, and its height growth 

 up to the fortieth year is very uniform. 



Table 2. — Comparative diameter, breasthigh, of the principal species for 



planting in eastern Nebraska. 



The stump was considered as a cylinder and the stem and branches as paraboloids. The 

 volume of the sample tree being known, the total volume of the group or class it represented 

 was obtained by the use of the following formula: V=vX-*^ in which V = volume of the 



whole group or class; v = volume of the sample tree: S = basal area of group or class rep- 

 resented by the sample tree; s = basal area of the sample tree. 



According to this table silver maple, honey locust, hardy catalpa, and 

 green ash make their best diameter growth during the first five years. 

 Cottonwood increases its rate of diameter growth from year to year up 

 to the fifteenth, and black walnut up to the twentieth. The rate of diame- 

 ter growth of the six species for the periods given is in the order named. 

 Hardy catalpa declines rapidly in diameter growth after the twenty- 

 fifth year, cottonwood and green ash after the thirtieth, and black walnut 

 after the fortieth. Honey locust and silver maple both show a fairly 

 uniform diameter growth to the end of the periods for which figures 

 are given. 



Heartwood composes the central portion of the stem, and may be 

 distinguished from the sapwood by a difference in color. It is harder 

 and more durable in contact with the ground than sapwood. The pro- 

 portion of heartwood to sapwood increases with the age of the tree. 

 Hence, when durability is required, old trees are more valuable than 

 young ones. 



