126 PEINCIPLES OF GARDENING. [CH. III. 



sensation. The texture of the membrane between 

 the meshes varies much in different species of plants. 

 In ver}' succulent plants, it is so contrived, tliat it 

 readily allows the absorption of moisture, but pre- 

 vents perspiration. Such plants are, consequently, 

 well qualified to inhabit hot climates and diy soils. 

 Neither is it at all impossible, that it possesses the 

 quality of allowing the passage of some gases, and 

 rejecting others, as the bladder of animals permits 

 water to pass through its textm'e, but is impendous 

 to alcohol. In old trees it cracks, and in many 

 cases becomes obliterated, the dead layers of bark 

 performing its offices. Its growth is slower than 

 that of other parts, and its powers of expan- 

 sion, though great occasionall}^ cannot equal the 

 rapid enlargement of the parts it incloses and de- 

 fends. This is very frequently the case with 

 the stem and branches of the cherry ; the tre€ 

 is then said by gardeners to be hide-hound, and is 

 relieved by making longitudinal incisions. It is 

 still more apparent in the fruit of the clierr}' and 

 plum : when rain falls abundantly during their state 

 of ripeness, their pulj) swells so rapidly, that in an 

 hour or two the epidermis of eveiy ripe dimpe upon 

 a tree ^^'ill be cracked. Gardeners are very prone to 

 scrape ^^ith no gentle hand the bark of their fruit- 

 trees ; whereas every care should be taken not to 

 wound its surface unnecessarily, and never to reduce 



