924 
Journal of Agricultural Research 
Vol. XXXI, No. 10 
In Figures 1 and 2 the data series just described are plotted, first 
with diameter at breast height and then with height as the inde¬ 
pendent variable. In Figure 1 each cross represents the average 
D.B.H.-INCHES 
Fig. 1—Curve of height over diameter breast high 
height of all the trees in a single 1-inch diameter class, the adjacent 
figure indicating the number of trees involved in each average. In 
Figure 2, similarly, each cross represents the average diameter at 
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Fig. 2 —Curve of diameter breast high over height 
breast height for all the trees in a single 10-foot height class. Each 
curve is quite strongly defined. Some surprise may be occasioned 
by the fact that the first of these curves falls after passing 13 inches 
