A STUDY OF HEART-ROT IN WESTERN HEMLOCK. rk: 
natural weakness in healing injuries, producing resin, etc., combined 
with environmental factors is responsible for the intensive and 
extensive fungous activity within this species of tree. At the same 
time it must be borne in mind, especially in the case of hemlock, 
that such a natural trait as the absence of any great amount of 
protective resin must be considered as playing an important part 
in the entrance of the disease. The foregoing data have clearly 
shown that one fungus is responsible for aimost the entire amount 
of heart-rot found in western hemlock, that the river-bottom type 
exhibits more decay than the other (comparing the youngest age 
class), that this type also exhibits a remarkably early decay, and 
that as a whole a large amount of heart-rot is found in hemlock at 
early periods in its life. 
Dense stands growing in moist, poorly drained soils develop a 
large number of suppressed or low-vigor trees: This is more com- 
monly the case when the stand is overtopped by older trees of 
other species. The low vigor due to the overshading of the lower 
crown causes the early and numerous formation of shade-killed 
branches. These in time produce branch stubs which are believed 
to be responsible for most infections by Hchinodontium tinctorium. 
The shading of the crown, especially the lower crown, not only 
causes the eventual formation of-branch stubs but produces a moisture 
and shade condition favorable to the germination and entrance of 
the fungus. As a theory of infection for hemlock types, this is 
corroborated by the fact that in thinnings made by cutting out the 
-more merchantable species the secondary crowns formed rapidly and 
vigorously by an enlargement and thickening of the regular crown. 
This fact, coupled with the observation that very few living sporo- 
phores were found 10 years after the thinning, strengthens the theory. 
DISCUSSION OF RESULTS. 
As a preliminary to the discussion of the main points brought out 
in the foregoing pages, it is essential to review briefly the main 
silvicultural characteristics of the tree in question. it will then be 
easier to point out the importance of the various factors influencing 
decay and to arrive at certain conclusions regarding the action of 
the fungus Echinodontium tinctoriwm during its life history on the. 
host. 
The western hemlock, as indicated by its dictabattane requires a 
cool and moist climate tion its development, and an important fact 
in this connection is its splendid maximum development along the 
western slope of the coast ranges, where it receives an annual rain- 
fall of from 70 to 100 inches.' 
1 Allen, E. T. The western hemlock. U.S. Dept. Agr., Bur. of Ferestry Bul. 33, p.10. 1902. 
