LARCH MISTLETOE. 



13 



tissues begin to form usually within a comparatively short time, from 

 one to two years in young plants. If the infection occurs on the stem 

 near the base of a branch, the cortical root system advances into the 

 bast tissues of the branch, initiating a burl or witches'-broom at that 

 point (fig. 1). The extension of the cortical roots upward along the 

 main trunk is sometimes sufficiently rapid to keep within the 4 to 

 5 year old portion of the stem, although the larch mistletoe seldom 



Fig. 10. — Cross 



action of a trunk of a larch tree with a large burl, showing its struc- 

 ture and a large pitch pocket. 



spreads very far from the point of original infection. The parasite, 

 however, usually travels more rapidly along the young shoots which 

 develop in number at the place of first infection. The spread of the 

 parasite outwardly along the branch or upwardly along the leader 

 may be hastened by the dissemination of seeds from the older infec- 

 tions. In this manner the last year's growth is often infected, and 

 even the terminal bud. The branches of the parasite eventually fall 

 away, leaving scars easily discernible on the older parts of the 



(%. i) 



