A STUDY OF HEART-ROT IN WESTERN HEMLOOK. ao 
contains. The total percentage of infected trees as well as the total 
rot percentage of this type in comparison to the slope site bear out 
this statement (Table III). The relation of moist sites to the degree 
of infection of a stand has been noted by Hartig,’ who says: ‘‘The 
climatic conditions peculiar to a given district may render it especially 
liable to outbreaks of certain diseases. Thus, in alpine districts 
proximity to lakes and narrow valleys specially predisposes to cer- 
_ tain fungoid diseases, because the moist air of such places favors the 
fructification of fungi in a high degree.”” The loss of vigor due to: the 
unfavorable environmental conditions and principally due to sup- 
pression by shade is responsible to a certain extent along with other 
factors in the rapid and universal spread of the decay on this site. 
Meinecke ? states: “The relative extent of decay by Echinodontium 
tinctorium is far greater in slow-growing, suppressed white firs than in 
thrifty ones.’ And in discussing the susceptibility of hemlock to 
injury Hanzhk and Oakleaf * state: ‘‘Broken branches and injuries 
to the bark account largely for the spread of conk (Trametes pini) 
and the stringy brown-rot (Hchinodontium tinctorium), these being 
more abundant in overmature stands and in suppressed stands over- 
topped by mature growth.” 
That on the river-bottom type the trees are decayed at an earlier — 
age, is brought out by a comparison of the data given. The river- 
bottom type in comparison with the slope type exhibits not only 
extensive decay at an earlier age and a younger age of infection but a 
larger number of branch stubs and sporophores for similar age classes 
for the stand. The data secured from the lumbermen of the north- 
western region also aid in determining the fact that hemlock is more 
defective on lower elevations, on bottom or flat sites, and on poorly 
drained soils. | 
In making use of pathological data in the determination of patho- 
logical cutting ages for a stand, the rot percentages as given here for 
separate age classes of the stand are of some value. With the rot | 
percentages as a basis (indicating the ratio of the rot volume to the 
total volume of the stand for each age class), the forester can deter- 
mine a cutting age for that stand, using all the economic and silvicul- 
tural factors to aid him in a correct determination. The average 
annual increase in rot volume between age classes can also be used 
to advantage in determining the rapidity of increase in rot volume. 
Forest pathology can thus serve to furnish pathological data for 
particular stands, which data can be applied by the practical forester 
1 Hartig, R. Textbook of the Diseases of Trees. Translated by Wiiliam Somerville, p. 10. London 
and New York, 1894. 
2Meinecke, E. P. Forest-tree diseases common in California and Nevada, p. 27. 1914. Published by 
U. S. Department of Agriculture, Forest Service. 
3 Hanzlik, E. J.,and Oakleaf, H. B. Op. cit. 
