ABNORMAL TISSUES. 125 



(Fig. 45) (to obtain cones, birds-nests, or to prune the tree) ; 

 or by exposure to the sun (sun-blister), hail, lightning, etc. 

 the injured cambium and wood is killed, while from the 

 surrounding healthy cambium and the parenchyma of the 

 wood and cortex, an occluding callus is formed, the abnormal 

 fibre-direction of which causes the wood to deteriorate. 



Pith-flecks are small occluding tissues that have closed old 

 wounds in wood. Such pith-flecks are common in the wood of 

 birch, alder and species of Pramis and I'irus : as they have a 



15. Injuri - i pinewood caused by climbing-irons, 



pathological origin, and may be absent, they should not be 

 used in the identification of these woods. [Stone, op. cit., 

 states that they are clue to short peripheral galleries made by 

 larvae, which are afterwards filled by parenchyma. Tr.] 



Resin-galls (Fig. 46) are flattish hollows within an annual 

 zone of coniferous wood filled with rosin and vary from an 

 insignificant size to the length of one's hand. When large and 

 numerous they have a prejudicial effect on wood and may be so 

 numerous as to render the wood unsuitable for planks, laths, etc. 



Tbe cause of resin-galls is explained by Mayr* as an 



* H. Mayr, "Das Harx der Nadelholzer." 18U4. 



