THE RUSTS 239 



cedar branches germinate and start a growth of mycelium 

 in them. There appear to be no uredospores and no 

 spreading of the disease to other apple trees by the aecidio- 

 spores. 



Consequently, in this case of the Cedar Apple and Apple 

 Rust we have but two distinct forms instead of the three 

 in the case of the Black Stem Rust. 



Thus: 



1 . Cedar Apples on Cedar. 



Teleutospores develop sporidia to go to apple leaves. 



2. Apple Rust. 



A. Sporidia cause mycelium that produces aecidia 

 containing aecidiospores. 



B. ^Ecidiospores go to cedar trees to develop cedar 

 apples. 



The mycelium in the cedar trees is perennial, living 

 from year to year and producing each season new cedar 

 apples to send out sporidia. Consequently, the destruction 

 of the cedar trees is helpful in preventing the development 

 of the Apple Rust. 



OTHER RUSTS 



The Orange Rust of blackberries, dewberries, and rasp- 

 berries is one of the most conspicuous and widespread 

 members of the family. It affects both wild and cultivated 

 plants and is found wherever these fruits grow. The con- 

 spicuous orange-colored aecidiospores appear in spring and 

 early summer, and are followed later by a crop of uredo- 

 spores, and these in turn by the teleutospores. The 

 prompt burning of all infested canes is very desirable. 



A characteristic leaf rust, known technically as Piiccinia 

 Pruni, commonly affects plums, peach, and other stone 



