194 



MAX UAL OF TREE DISEASES 



jelly-like and the individual spores germinate, each producing 

 several secondary spores (basidiospores) which are shot off into 

 the air. These spores are carried away by the wind and may 

 find lodgment on the leaves, twigs or fruit of the proper alternate 

 host. Under favorable conditions of moisture, the basidiospores 

 germinate and the tissue of the pomaceous host is penetrated 

 and a new growth of mycelium started. The area of tissue 



invaded is limited 

 to a small spot 

 which becomes 

 somewhat swollen 

 and light yellow in 

 color (Fig. 29). A 

 short time after 

 these symptoms 

 become apparent, 

 long whitish tubes 

 of fungous tissue 

 are pushed out all 

 over the affected 

 areas (Fig. 30). 

 These tubes some- 

 times spht and 

 form a fringe 

 around cup-like depressions in the leaf, twig or fruit, in which 

 are formed powdery masses of yellow spores (seciospores)-. 

 These dust out, are borne by the wind and may continue the 

 life history of the fungus if they lodge on the leaves or twigs 

 of the proper species of juniper or cedar. 



These rust-fungi are important because they deform the tree 

 when galls, witches'-brooms or cedar-apples are formed in abun- 

 dance. The tissues of the affected branches die eventually and 

 leave dead areas where wood-rot fungi may enter. On the 

 apple-like hosts, which include not only many important cul- 



FiG. 29. — Cedar-apple fungus on wild apple leaves. 



