A STUDY OF HEART-ROr IN WESTERN HEMLOCK. 27 



formation. The swaying of the trees b}^ the wind when the low 

 temperature has set up a stress within the tissues of the lower trunk 

 would cause the cracks to form at right angles to the swaying move- 

 ment and in the root-spur hollows, where the least resistance to 

 splittmg was to be encountered. The swaying of the tree alone 

 sets up varying forces of strain and rupture in the lower part of the 

 tree, and when the tissues are contracted or prevented by low tem- 

 peratures from adjusting themselves, a frost crack eventually occurs. 



Sporophores of fungi, if they develop at all, appear after a certain 

 period has elapsed from the time of first infection. This period, up 

 to the present time, has not been determined for most of the xyloph- 

 ilous fungi, at least not for EcJiinodontium tinctorium. Such deter- 

 mination would involve a considerable amount of careful inoculation 

 work upon trees absolutely free from fungous infection, which in the 

 case of wood-destroying fungi would extend over a period df several 

 years. The relation which sporophores bear to the development of 

 decay in the host and to the degree of infection can more easily be 

 determined. A careful field study of the tree in question with 

 reference to recording all possible data relating to the sporophores 

 has developed several interesting facts. Little work has been done 

 along this line tending to give actual figures as a basis for con- 

 clusions. The data collected are grouped under the two parts of 

 Table V for the river-bottom and slope types, respectively. Under 

 the heading "Position on tree/' the sporophores were grouped to 

 indicate whether the northerly growing sporophores were more 

 numerous than those growing on the southerly side of the tree. The 

 remaining columns in Table V are self-explanatory with the excep- 

 tion of the column headed "Relative position along trunk." This 

 refers to the vertical position of the largest sporophore with respect 

 to the other sporophores on the same tree. For example, tree 

 No. 50 had a total of five sporophores, of which the third one from 

 the ground was the largest. This condition was expressed by the 

 figures 3-5, indicating that the position of the largest sporophore 

 was in the center of the group. This method was used throughout, 

 and the resulting figures were used to determine whether the largest 

 sporophore was found more commonly in the center or toward either 

 end of the group. 



The river-bottom type with reference to its sporophore data 

 (Table V) is in general very similar to the slope type. Out of a 

 total of 119 trees, 70 (59 per cent) were sporophore-bearing trees. 

 On these 70 trees a total of 149 sporophores were found, of which 

 131 (88 per cent) were living and 18 (12 per cent) were dead, giving 

 an average of 1.8 live sporophores to a tree and 1 dead sporophore 

 to every 4 trees. These figures show a much larger percentage 



