i6o 



Bulletin 272. 



from the body and limbs of the trees the BHght finds conditions most 

 favorable. Introduced by an insect into the tip of one of these succulent 

 shoots, the parasites multiply rapidly and appg.rently become more 



Fig. 16. — Cankered limh showing exuding milky drops. The sticky sap 

 is made tip almost entirely of the bliglit bacteria. 



virulent as they proceed downward, finally reach the limb of the tree 

 and spread about the base of the shoot into the bark. Cankers are 

 usually formed about the base of the blighted blossom-spur or water- 

 sprout (Fig. 17). Some of these cankers, as pointed out above, serve 



