78 THE HEALING OF WOUNDS 



drical, and why the old bark becomes marked 

 with furrows, scales and plates. 



If, for any reason, the bark should become so 

 dense and strong that the trunk cannot expand, 

 the tree is said to be "bark-bound." Such a 

 condition is not rare in orchard trees which have 

 been neglected. When good tillage is given to 

 such trees, they may not be able to overcome the 

 rigidity of the old bark, and, therefore, do not 

 respond to the treatment. Sometimes the thin- 

 ner-barked limbs may outgrow in diameter the 

 trunk or the old branches below them. The 

 remedy is to release the tension. This may be 

 done either by softening the bark (by washes of 

 soap or lye), or by separating it. The latter is 

 done by slitting the bark -bound portion (in 

 spring), thrusting the point of a knife through 

 the bark to the wood and then drawing the 

 blade down the entire length of the bark -bound 

 portion. The slit is scarcely discernible at first, 

 but it opens with the growth of the tree, filling 

 up with new tissue beneath. Let the reader 

 consider the ridges which he now and then finds 

 upon trees, and determine if they have any sig- 

 nificance. In other words, are the trunks of 

 trees ever perfectly cylindrical ? If not, what 

 may cause the irregularities f Do trunks often 

 grow more on one side than the other? 

 Slit a rapidly -growing limb, in spring, with a 

 knife blade, and watch the result during the 



