130 PRINCIPLES OF GARDENING. [CH. III. 



solution of lime, which, however efficient in the de- 

 struction of moss, is not so in the removal of insects 

 — is highly injurious to the trees, by filling up the 

 respiratory pores of the epidermis, and is decidedly 

 a promoter of canker. Let my remedy be brought 

 by every orchardist to the test of experiment under 

 his own eye, that it may be effectually done, and he 

 will not require me to theorise. Facts are stubborn 

 opponents. 



The injury inflicted by stopping the pores of the 

 epidermis, on the stem and branches of a tree, is at 

 once evident from the fact, that oxygen and water 

 are absorbed, and carbonic acid evolved from them, 

 the same as in the leaves, which operations are all 

 parts of the process of elaborating the sap. It is no 

 trivial inspiration of oxygen ; for in twenty-four hours, 

 the branch of an apple-tree has been found to inhale 

 five times its own volume. 



If the fibres emitted by the ivy, by which they 

 cling to other trees for support, do not aid it in ob- 

 taining nourishment, yet by fillmg their respiratory 

 pores, they ai'e injurious, and should never be al- 

 lowed to cling around serviceable trees. 



Immediately beneath the bark is situated the wood, 

 which forms the chief bulk of trees and shrubs. It 

 is formed of concentric layers, one of which, at least, 

 is added annually. These layers are formed of a tissue 

 of longitudinal fibres, resembling net-work, the in- 



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