30 BULLETIN 722,-U. S. DEPARTMENT OF AGRICULTURE. 
The distance from the ground of the largest sporophore ranges 
from 4.5 feet in the case of younger suppressed trees to 78.5 feet in 
the case of a large 300-year-old veteran. The average height in- 
dicated 39.9 feet. The grouping of the sporophores in respect to 
their cardinal positions on the tree gave some very interesting 
figures. The largest number of the sporophores (38 per cent) was 
found in the northwest to north-northeast grouping, 27 per cent in 
the southwest to south-southeast, and 21.5 and 13.5 per cent in 
the west and east groupings, respectively. Upon dividing the 
sporophores into groups corresponding to the eight principal points 
of the compass, it was found that 25 per cent were on the north 
side, the next largest on the west (21 per cent), and the smallest 
number on the southwest (4 per cent). The data for the slope type 
show the largest number on the northerly side of the tree. No 
such overwhelming percentage was secured as in the work of Mdller,! 
who assembled data on the sporophores of Trametes pini (Brot.) Fr. 
and found that 45.8 per cent of the sporophores appeared on the 
west side of the tree and 89.4 per cent on the westerly side. This 
westerly side included all sporophores listed in the north, south, and 
west columns. 
Figure 12, the southwestern-slope type, represents in the respec- 
tive column the sporophore data taken from Table V. The same 
relation is found to exist between the degree of infection and the 
total number of sporophores as is found in the river-bottom type. 
The number of sporophores per 10 trees ranges from 13 in the 41 to 
100 age class to 24 in the 101 to 160 age class, exhibiting a con- 
siderable increase between the two. In the slope type a similar 
rate of increase can be noted, which is constant between all the age 
classes except the two oldest. 
THEORY OF INFECTION. 
Suppression caused by shade combined with a crowded condition 
of root spacing as well as crown spacing tends to reduce vigor appre- 
ciably. A poorly drained soil having a large amount of soil moisture 
is another factor to be considered in this connection. 
Upon the vigor of a tree depend all its vital functionings, its ability 
to enlarge and elevate its crown toward better lighting, to secure 
raw material and manufacture food, to compete with its neighbors, 
to quickly heal wounds, and to resist attack by fungous enemies. 
The predisposition or inherent susceptibility of a tree to disease is 
not considered a sufficient cause for the extensive attack and devel- 
opment of a fungus in that tree. It is believed that low vigor or a 
1 Moller, A. Uber die Notwendigkeit und Méglichkeit wirksamer Bekiimpfung des Kiefernbaum 
schwammes Trametes pini (Thore) Fries. Jn Ztschr. Forst. u. Jagdw., Jahrg. 36, Heft 11, p. 677-715, 2 
pl. (partly col.) 1904. 
