LARCH MISTLETOE. 17 



developing a " spike top " (figs. 4, 6, and 7) . All heavily infected trees 

 by the time they have reached the age of 200 years, if they succeed in 

 living to that age, have developed a "spike top" (Table II). 



Occasionally infected trees attain a considerable size, due to the 

 fact that the original infections occurred chiefly at the bases of the 

 branches and did not spread. The attendant broom formation oc- 

 curring on the branches next to the trunk allows the retention of the 

 branches for a longer time than if brooms were developed farther out 

 on the branch. The merchantability of the tree is greatly reduced, 

 however, by the formation of a series of basal branch burls, causing 

 streaks of pitchy wood to extend along the trunk from one burl to 

 another. 



The spread of the parasite in the direction of the prevailing winds 

 was very interestingly shown in a number of cases. One case in 

 particular was noted in which a series of trees of nearly the same age 

 standing in a row extending in the general direction of the more con- 

 stant winds indicated that the infection had gradually traveled from 

 the first and most seriously infected specimen to those least infected 

 at the other end of the row. These trees had apparently originated 

 under the protection of an old windfall. Since there were no in- 

 fected trees immediately to the right or left, it is fairly evident that 

 the wind was a factor in seed distribution and also determined the 

 direction of distribution. In order to appreciate thoroughly the 

 significance of the effects of mistletoe on the larch, a study should be 

 made of figures 3, 4, 6, and 7, representing different stages of sup- 

 pression and various types of infection. 



On the drier slopes, from 80 to 90 per cent of the larch of all ages 

 has been found infected. On the more favorable sites, the percentage 

 of infection was very low and therefore did not interfere seriously 

 with the best development of the species. (See trees Nos. 40 and 41, 

 Table II.) 



After the preliminary survey, and in order to answer definitely the 

 question whether or not mistletoe is as great an enemy to the host 

 as outward appearance seems to indicate and to obtain, as near as 

 possible, comparable figures on mistletoe injury, 45 infected and 

 uninfected trees were cut and such measurements taken as were 

 thought necessary for the needs of the problem in hand. These data, 

 along with many other observations having a bearing on the subject, 

 have been arranged in Table II, whereby it is possible to follow out 

 the main factors operative in the deterioration or suppression of the 

 trees studied and by means of which fairly conclusive comparisons 

 may be drawn. 



