WOUNDS 247 



causes the cortex dies, and growth ceases at the injured spot 

 But more than that, the dead cortex remains for a long time in 

 union with that which is living and uninjured, and no formation 

 of callus can take place, because growth is stimulated along the 

 edge of the wound only when the bark-pressure is reduced. 

 The formation of wound-rot is encouraged by water collecting 

 behind the dead cortex, which becomes locally fissured owing to 

 shrinkage consequent on drying, and finally rots away, but only 

 after the lapse of many years. 



WOUNDS CAUSED DURING THE COLLECTION OF RESIN 



Turpentine and resin are procured from conifers in various 

 ways. In the case of the silver fir, it is only the turpentine 

 that is gathered. This collects in vesicles in the cortex, which 

 sometimes attain to the size of a pigeon's egg (Strasburg 

 Turpentine). 



In the case of the larch, large holes are bored into the stem, 

 and these being afterwards plugged up collect the "Venetian 

 Turpentine " which flows down from the vertical resin-ducts of the 

 wood. In the case of the black Austrian pine, the cortex is 

 removed from the stem in fairly broad stripes, the turpentine 

 that exudes freely from the canals of the medullary rays being 

 collected in a receptacle that is cut in the stem below the 

 wound, while the resin is scraped from the wound after it has 

 solidified. On account of the exposed wood soon becoming 

 impregnated with resin, and the canals of the medullary rays 

 becoming choked up with the same substance, it is necessary 

 from time to time to remove fresh portions of cortex at higher 

 points on the stem. 



In the case of the spruce, vertical strips of cortex, one to two 

 inches in breadth and extending from the base of the stem to a 

 height of about six feet, are detached from the tree. When the 

 tree is small the resin is taken from one side only, but as it gets 

 thicker four sides may be utilized (Fig. 142). When the flow of 

 resin ceases, the callus that has been formed along both sides of 

 the wound since the last time of stripping is removed, and thus 

 a new set of resin-ducts is opened, from which resin continues 

 to flow. 



