27 



away, the sap will be sure of being em- 

 j)loyed to some other good purpose ; for 

 every useless branch, like every noxious 

 weed, should be put out of existence. 

 When we turn our attention to the first 

 principles of vegetation, we observe, that 

 the roots of every tree are intended to im- 

 bibe from the soil a certain quantum of 

 food, which is taken into the tree to form 

 its different parts, and in so doing a 

 limited quantity is prescribed to each 

 kind. The traveller's joy, which grows 

 very quickly, and is supported by other 

 plants, does not require, nor in fact has 

 it, so much, as the hazel on which it 

 is supported. Neither does the rasp- 

 berry, which only exists in its lignoeus 

 or tree state for a few^ months, require 

 that quantity which the oak tree does, that 

 is to last for ages. For if we compare 

 them together, we shall find, on cutting 

 pieces of each transversely, that of the 

 raspberry to consist only in a mass of pith, 

 surrounded by a thin cylinder of fibrous 

 membrane just enough to enable it to 

 stand upright, and support the fruit. The 

 c ^ 



