116 THE HEALING OF WOUNDS 



THE MENDING OF TREES 



Plants are exposed to injuries of storm, weather- 

 ing, and animals, and to the disasters which result 

 from the struggle for existence ; and they are 

 maimed by careless pruners and workmen. Many 

 of these injuries can be repaired, and the preced- 

 ing discussions will help us to understand how. 

 A few cases may be explained, however, as a 

 means of further elucidating the subject. 



Label wires were carelessly left on the trunks 

 of young trees. The re- 

 sults are seen in Figs. 95 

 and 96. It will be noticed 

 that the larger diameter is 

 above the girdle. This is 

 easy of explanation. We 

 have already found (page 17) that 

 the materials taken in by the roots 

 are not directly available or useful 

 in the making of plant tissue. They 

 ascend to the leaves, and are there 

 95. The mischiev- elaborated, in connection with ma- 

 ous label wire, terial taken from the air, into organ- 

 ized compounds, or become incor- 

 porated with such compounds. These organic 

 compounds of which starch is the chief are 

 transferred to every part of the plant to build 

 up its tissues. The transfer takes place in the 

 inner layers of bark; therefore, whatever food 



