i68 



DISEASES OF TREES 



shoot bends over a little at the place occupied by the spore-layers. 

 In many cases, however, the ultimate contortions, which have 

 earned for the parasite the designation Pine Twister, C. 

 pinitorqumn, are due to the weight of the young shoot, whose 

 apex, in the case of lateral branches that are considerably 

 damaged on one side, is bound to be depressed. Later on the 

 apex again grows up, and thus S-shaped contortions arise. If 

 the weather is normal, a few such sporophores are formed 



FIG. 99. Apex of a pine which has been attacked by C. pinitorquum. The leading 

 shoot has been killed almost to the base. The branches of the whorl, as well as 

 the main shoot-axis, show diseased spots and contortions which have existed for 

 a considerable time. 



annually on the young shoots, while in very dry weather the 

 sporogenous layers wither up as soon as formed, and no external 

 damage is visible. Should May and the beginning of June be 

 very wet, the sporophores develop so abundantly and luxuriantly 

 that the shoots, with the exception of the base, die off and dry 

 up completely (Fig. 99). A badly diseased young Scotch pine 

 wood appears in the end of June as if a late frost had killed and 

 contorted all the young shoots. Next year the dormant eyes 



