356 PRODUCTS OF THE FOREST AND WOOD LOT 



FIG. 247. Pruning and tree surgery: 1. a, heart wood; b, sap wood; c, cambium or 

 growing layer; d, inner bark; e, outer bark. 2. When a large limb is cut it should be sawed 

 very close to the body so that the growing layer and bark can produce a new growth to cover 

 it. The cut surface should be painted to prevent decay. 3. A new growth over an old 

 wound leaves a deep hole at the center if decay begins too soon. 4. A cross section showing 

 the affected part. 5. The growth in many cases may continue and almost or entirely hide 

 the affected part. 6. A section showing the decayed heart wood commonly known as "hol- 

 low tree." (U. S. D. A.) 



