A STUDY OF HEART-ROT IF WESTERN HEMLOCK. 19 



In order to determine the distribution of EcMnodontium tinctorium 

 and the extent of the damage produced by it as influenced by various 

 environmental factors, a series of questions was prepared and sub- 

 mitted to the timber and mill owners in all parts of the Northwest. 

 In response to a total of 151 letters sent out, 44 replies dealing with 

 hemlock were received. A certain number of the replies were con- 

 fined to grand fir alone. The replies to the questions were prepared 

 by experienced scalers and cruisers, to whom the writers desire to ex- 

 press their thanks for the careful attention and willingness shown to 

 further the progress of the investigation. In most cases the " conks'^ 

 (figs. 1, 2, 3, and 4) of the fungus chiefly responsible for the decay in 

 hemlock for the region were sent by the recipients of the letters. In 

 practically every instance the fungus was E. tinctorium. Many of the 

 northwestern regions not covered by these letters were visited; hence 

 it was possible to gain a fairly accurate knowledge of the range and 

 destructiveness of this disease along with the data on other phases of 

 the study. Since the questions given out dealt with a variety of 

 factors, the information thus obtained is submitted under the various 

 sections of this paper covering the particular point under discussion. 

 Four of the questions concerned the influence of site on the distribu- 

 tion and prevalence of decay. 



The belief that conditions of soil, moisture, exposure, and altitude 

 greatly influence the distribution and prevalence and the amount of 

 decay caused by a particular fungus in the forest is supported by the 

 data thus obtained. Out of 44 different observations covering a 

 great range of territory, includmg the entire economic range of the 

 tree in the United States, only three observers report a uniform dis- 

 tribution of decay in hemlock for all conditions. All other replies 

 indicate great differences in the amount of heart-rot as influenced by 

 soil, slope, and elevation. The topography and soil of those regions 

 from which a uniform condition of defect is reported are so uniform 

 in themselves that no great variation could be expected. The ques- 

 tion of the influence of the site on the prevalence of the fungus 

 EcJiinodontium tinctorium, it appears, depends on the moisture condi- 

 tion of the soil and its porosity and not upon soil quality. The fimgus 

 may occur on hemlock growing on any type of soil, but occurs to a 

 greater extent on trees growing on wet, undrained sites. This is 

 found to be true at any elevation, showing very clearly that the ex- 

 cessive moisture conditions of the site are highly favorable to the de- 

 velopment of the principal attacking fungus. The answers indicate 

 that the soundest hemlock is usually associated with a rich, well- 

 drained soil. In wet, shallow soil the root system can not attain its 

 normal position but must stay near the surface. If the soil is suffi- 

 ciently loose to enable the roots to penetrate deeply, but is undrained, 



