10 



BULLETIX 317, U. S. DEPARTMENT OF AGRICULTURE. 



deteriorating agents and eventually dies before reaching its maxi- 

 mum development (fig. G). The radial dimensions of the last annual 

 ring of trees in the final stages of mistletoe suppression (fig. 7) 



Fig. G. — A larch tree in the last 

 stages of mistletoe suppression. 

 A few of the -witches'-brooms 

 contain living branches. The 

 tree was making no percepti- 

 ble increment and was far be- 

 low the normal size for the 

 region. It was necessary to 

 clear away from the base of 

 the tree the heap of fallen 

 ■witches'-brooms before it could 

 be cut. 



same time is followed up 

 responds favorably to the 

 species must necessarily foil 



Fig. 7. — Two larch trees barely living, as evi- 

 denced by dissection of the bole. Note the 

 very large witches'-brooms and numerous dead 

 branches. 



were often so fine and narrow that they 

 could be counted only with the aid of a 

 compound microscope. In some of the 

 worst cases the tree was able to produce 

 but a single layer of tracheids in a year. 

 In so far as climate influences the 

 prevalence and destructive effects of the 

 larch mistletoe, that of the Blue Moun- 

 tain region is most favorable. It might 

 be here added that when a particular 

 tree species has succeeded in establish- 

 ing itself outside of what may be con- 

 sidered its optimum range and at the 

 by a most destructive parasite which 

 habitat, the rapid deterioration of the 

 ow, at least in the more unfavorable sites. 



