REGIONAL VOLUME TABLE 



729 



decision as to how many tables should be prepared and how the local- 

 ities should be grouped for this purpose. 



It has been noted in previous work in other species that frustum 

 form factors varied with diameter only and not with height. Con- 

 firmation of this not-entirely proved theorem was therefore sought in 

 the largest group of white fir measurements. Table 4 gives these 

 factors by both height and diameter classes. 



The values (uncurved) are, of course, decidedly irregular and there 

 is a large variation within each diameter class, but there seems to be 

 no constant relation between these variations and height. Considering 

 only those diameter classes where there are more than three values, 

 in two the factors appear to increase with an increase in height, in 

 two, to decrease, while in fourteen, they rise and fall irregularly. The 

 hypothesis of the preceding paragraph therefore, seems to be con- 

 firmed and the use of a single frustum form factor for each diam- 

 eter class to be justified. 



Table 5 shows the factors thus worked out for each group after in- 

 creasing the size of the diameter class so as to get more regular figures, 

 but without averaging the results by curves. 



Fig. 1. — Frustum form factors of white fir for diflferent localities. AA — Stan- 

 islaus (1); BB— Stanislaus (2); CC— Crocker ; DD— Plumas, Tahoe (A); 

 EE— Ellis Meadow; FF— Plun as, Tahoe (B) ; GG— Deer Camp; HH— Smith 

 Mill. 



These values were next evened off by curves, the results appearing 

 in figure 1. The differences in curve form are rather surprising and 



