2i8 TIMBER AND SOME OF ITS DISEASES. [CHAP. 



interesting histological questions connected with this 

 callus-formation, or with the mechanical relations of 



FlG. 32. The same in longitudinal section : lettering as before. Six new layers of 

 wood have been developed, and the cut end of the branch was completely 

 occluded before the last three were formed i.e. at the end of 1885. After that 

 the cambium became once more continuous round the whole stem, and, beyond a 

 slight protuberance over the occluded wound and the ragged edges of the dead 

 corky outer layers, , there are no signs of a breach. 



the various parts one to another. It is sufficient for 

 our present object to point out that this process of 

 covering up, or occlusion, as I propose to term it, 



