HAWTHORN CLUSTER-CUPS 



255 



and form a mycelium on branches of juniper, where they 

 give origin to the first or teleutospore stage of the fungus. 



Fig. 65. Gymnosporangium clavariaeforme. i, teleutospore 

 stage on branch of juniper ; 2, teleutospores, x 300 ; 3, teleuto- 

 spores germinating and producing secondary spores a a, x 300; 

 4, aecidium stage on pear leaf; 5, aecidium stage on branch, 

 leaves, and fruit of hawthorn ; 6, aecidiospore germinating, x 300. 



The aecidium stage of the fungus is often very injurious to 

 nursery stock, frequently nearly every leaf on the tree being 



