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, dnd 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 MoUer/ 

 who assembled data on the sporophores of Trametes inni (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 dec 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 



' MdUer, A. tjber difi Xotwendigkeit iind Moglichkeit wirksamer Bekampfung de? Kiofernbauiri 

 schwamraes Trametes pint (Thoro) Fries, hi Ztschr. Forst. ii. Jagdw., Tahrg. 36, Helt 11, p. f>77-7ir,, 2 

 pi. (partly col.) 1001. 



