6 BULLETIN 199, U. S. DEPAKTMENT OE AGRICULTURE. 
the white-pine study as were secured for the hemlock study, 1 and all 
available factors were taken into consideration in the final results. 
Forest descriptions were written for each sale area, and notes were 
made of the moisture and shade conditions existing on each. 
The data obtained from a total of 1,417 trees, of which 135 were 
grand fir (Abies grandis), were first arranged according to site and 
age class. While in the field it was found that the number of trees 
needed in the two youngest age classes could be considerably reduced 
from the 100-tree standard. It was found that the trees on the 41 
to 60 age class in both types of sites, slope and bottom, were uni- 
formly free from visible decay. Owing to this condition and to the 
fact that young white pines of this age class are too small to be 
merchantable and should not be cut needlessly, it was decided to 
reduce the number of trees required. In the 61 to 80 age class it 
was found that the rots were in the beginning stages, and 60 trees 
per age class for each type of site were considered sufficient. In all 
the other age classes the number of trees was either above or but 
slightly below the 100 mark, except in the 121 to 160 age class on 
the slope sites, where the number was doubled in order to make a 
comparison between a similar age class and site for two widely 
separated sale areas, and in the 201+ age class, where it was impos- 
sible to find more than the recorded number of trees. There was, 
fortunately, one sale area which furnished a fairly large number 
of trees of the very old age class (201+ ). 
Tables were prepared from the data collected, and these will be 
presented in the order of their consideration in the text. The 
volumes were figured by means of the Smalian formula. In these 
tables the word " Infected " as used at the head of certain columns 
is intended to cover all trees visibly infected. Early stages of 
infection not determinable by field observations and not measur-, 
able as recognized cull are not included. 
RELATION BETWEEN ROT AND VARIOUS FACTORS. 
AGE. 
In Table I are found the data which show the relation between the 
rot volume and the age class of the stand. These data are separated 
under heads of "Bottom sites" (upper part of table) and "Slope 
sites" (lower part of table), and the data under each head are 
grouped according of the seven principal age classes. 
Trunk-rot, indicated in the table by the initials T. E., represents 
mainly Trametes pint. Butt-rot, indicated by the initials B. R., 
represents Trametes pint when acting as a typical butt-rot. but in- 
1 Weir, J. R., and Hubert, E. E. A study of heart-rot in western hemlock. U. S. 
Dept. Agr. Bui. 722 r 39 p., illus. 1918. 
