Trees and Timber 



377 



prevent further inroads by 

 fungi already established 

 in them. The real value 

 of surgical treatments is 

 somewhat problematical. 

 The practice is of compar- 

 atively recent popularity, 

 and a long interval of time 

 is necessary to determine 

 the amount of benefit. 

 The procedure is as fol- 

 lows: First, all decayed, 

 diseased, or injured wood 

 or bark must be removed, 

 either by severing a limb 

 entire or by cutting out 

 a cavity, in which case 

 a mallet, sharp gouges, 

 chisels, and a knife are 

 needed. To reach all of 

 the diseased wood it is 

 usually necessary to en- 

 large the opening and fre- 

 quently to make one or 

 more holes above or be- 

 low the main opening, or, 

 what is perhaps better, to 

 cut a narrow opening of 

 the required length. The 

 excavation should be en- 

 larged in all directions 

 until only sound, unin- 

 fected wood is left. The 

 bottom of the cavity 

 should be so shaped as 

 to provide drainage. The 

 edges of the cavity should 



Fig. 198. — Detailed view of exca- 

 vated and bolted cavities. Above 

 cross-section of a young tree trunk 

 showing how the new wood and 

 bark grow into an unfilled cavity 

 from the margin. (The line on the 

 wood indicates the amount of ex- 

 cavating that would be needed be- 

 fore filling the cavity.) 3. — Cross- 

 section of a tree trunk showing 

 the manner of using two single- 

 headed bolts to brace a cavity. 

 After Collins. 



