PREVENTION AND REPAIR OF MECHANICAL INJURIES 139 



trees as poplar has extended over even board fences fastened 

 to them. Figure 97 shows an oak tree which has grown 

 around the end of a bench at Hunter's Park, Pennsyl- 

 vania.* Label wire injuries are always due to careless- 

 ness or ignorance. At 

 planting time the wire 

 is left encircling the 

 trunk of the newly set 

 tree. Because it is 

 loose it looks harmless, 

 but when the tree 

 grows it soon begins to 

 cut the trunk and to 

 check the flow of elab- 

 orated sap from the 

 leaves downward. Cop- 

 per wire, the kind usu- 

 ally employed by nurs- 

 erymen, is especially 

 pernicious because it 

 lasts much longer than 

 does iron or string. 

 \Vhen the wire is on 

 the main trunk its in- 

 jury may be so severe 

 as to kill the tree; 

 when on a branch, it 

 may cause an abnormal 

 development (Fig. 95). 

 Generally the trunk 

 becomes larger above than below the girdle (Fig. 96)V 



Label wire and other girdles are not necessarily fatal 

 to the trees so injured (-Fig. 96). As long as the sap 



* A similar case is pictured in Popular Mechanics, March, 1916. In this case 

 the trees grew around the boards of a fence. 



FIG. 97 . ; 



BENCH SUPPORTED BY LIVING TREE 



Originally there were upright supports 

 beneath the bench, but these have rotted, 

 away. The board, not being in contact .with 

 the soil and being quickly dried after, rains,, 

 continued sound and rigid. The bark there- 

 fore grew around the end as seen. The tree 

 at the other end of this bench shows similar 

 growth, and on its opposite side shows where, 

 another board was similarly buried but has. 

 been destroyed by fire, leaving a slot 4 inches 

 deep where the bench originally met the trunk. 





