41 



pletely girdling small branches. As a rule, a thickened, irregular margin of living 

 bark forms round the wound, giving a ragged appearance to the parts attacked, 

 and very characteristic of the disease." Spores (conidia) are borne in autumn on 

 minute white cushions on the wound, and in spring ascospores are produced in 

 small red perithecia, situated on the same cushions. Small white stromata appear 

 in the fall and produce minute conidia (ovate-oblong, one-celled 7 x 3|"). In 

 the following season pale stromata appear and produce larger conidia (sickle-shaped 

 and pluri-septate — the Tubercularia stage). Perithecia develop later in dense 

 papillate bright red clusters on the edges of the wound. Asci are cylindric, 8- 

 spored; spores ovate oblong, 1-septate, 14 x 5-6". 



Bitter-Rot Canker (Glomerella rufomaculans). — This canker is very com- 

 mon in the orchards of Illinois and other central States. The relationship of this 

 canker to the Bitter-Rot was discovered in 1902, when it was determined that the 

 winter stage was passed on the cankers formed on the branches and often at the 

 base of the old fruit-spurs. It was also proven that the main source of infection 

 of the fruit was this winter and permanent stage of the disease in the canker. 



Bitter Rot Canker (after Burrill). 



This canker is most usually found on small branches, and starts from a bruise on 

 the bark. "Growth takes place around the diseased area as it does about any 

 wound, and there is found an irregular encircling rim of healing tissue about a 

 dead and depressed, or sunken, usually elongated black patch, covered with dead 

 bark." (Figs. 2 and 3). It injures fruit as well as branches. On the fruit it 

 was long known as Gloeosporium fructigenum. The mycelium is present in the 

 bark and cambium and the pustules break through the bark. The conidia are hya- 

 line, ovate to oblong, 12/16 x 4/6", and germinate readily. The perfect stage 



