216 TIMBER AND SOME OF ITS DISEASES. [CHAP 



layers of wood and cortex with cambium between 

 them (Fig. 30) ; and it will be noticed that each year 

 the layer of wood extends a little further over the sur- 



FIG. 30. The same in longitudinal section ; P, S, and C as before. The four new 

 layers of wood formed during 1879-82 are artificially separated from the preced- 

 ing by a stronger line. On the left side of the figure it will be noticed that the 

 cambium (and therefore the wood developed from it) projected a little further 

 over the cut end of the branch each year, carrying the cortical layers ( C0r)vfilh 

 it. At +, in both figures, there is necessarily a depression in which rain-water, 

 &c., is apt to lodge, and this is a particularly dangerous place, since fungus- 

 spores may here settle and develop. 



face of the wood of the wound, and towards the 

 centre of the cut branch ; and in course of time, 



