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These areas begin as slight discolorations, which liecome tlepresserl, and a 

 distinct crevice marlvs the line between the healthj' and diseased bark. 

 The bark may fall, exposing the wood, or it may adhere closely to the 

 underlying wood. A plate of cork seems to limit for a time the extent 



Fig. 1. Twenty Ounce apple tree dying from the attacks of New York apple tree canker. Note 

 the characteristic dying out of the top. 



of the diseased area, but this is pierced and the healtliy tissue invaded. 

 Soon the affected cells are killed; they shrink, and the healthy portion 

 again is separated from the diseased by a crevice and by a second plate 

 of cofk. This process cniitinues until we have concentric rings as shown 



