Drupaceous Fruits 89 



On many plants crown-gall is practically harmless, while 

 on others, especially the fruit and nut trees and the cane 

 fruits, it is injurious. The chief injury seems to arise from 

 the fact that crown-gall paves the way for the entrance of 

 rot-producing parasites, interferes with proper root develop- 

 ment and the conduction of foods and water. Whatever 





Fig. 45. — Cracked peach, caused by Pseudomonas 

 ■pruni. Advanced stage on fruit nearly ripe. 

 After Roberts. 



may be the actual mode of producing injury, the fact is well 

 estabHshed that trees with crown-gall do not, in general, 

 develop or yield as well as trees without galls, though in rare 

 cases, trees with crown-gall may fully equal ungalled trees. 

 All diseased stock should be avoided, as well as stock from 

 nurseries where the disease is known to exist. Care on the 

 part of nurserymen to use soil free from crown-gall; to avoid 

 wounding the young trees and to make close-fitting grafts, 

 and protect them well with wax, will lessen infection. 



