226 DISEASE IN PLANTS. 



thickening rings all round the axis of the bud 

 except at the extreme apex. When the separa- 

 tion occurred the cambium of the wood beneath 

 covered over the previous point of junction, and 

 thus the woody bud was pushed out with the 

 bark, and now protrudes covered with a thin 

 layer of the latter. Similar nodules are occa- 

 sionally found on Apple trees. 



Notes to Chapter XXIV. 



For further information on Cankers the student should read 

 Marshall Ward, Timber and some of its Diseases^ Chapter X. 

 Further, the discussion as to the causes of canker in Frank, 

 Krankheiten der PJIattzen, B. I., p. 207, and B. III., pp. 167 

 and 172, and various papers in Zeitschrift fiir Pfla7izen- 

 krankheiten. 



