SECT.' VIII. DESCENT OF PROPER JUICE, 



endeavours to establish by tbe following analogies : 

 if the blood escapes from the vessels of the animal 

 body, it forms neither flesh nor bone, but tumors ; if 

 the proper juices of the plant are extravasated, they 

 form neither bark nor wood, but a lump of gum, 

 resin, or inspissated juice. The disruption of the 

 blood vessels and consequent loss of blood, injures 

 and often proves fatal to the animal. The extra- 

 vasation of the proper juice injures and often proves 

 fatal to vegetables, unless the evil is prevented by 

 the skill and management of the gardener. What- 

 ever may be the value of these remarks as tending 

 to establish the analogy in question, it cannot be 

 doubted that the cambium or proper juice consti- 

 tutes at least the grand principle of vegetable 

 organization ; generating and developing in succes- 

 sion the several organs of the plant, or furnishing 

 the vital principle with the immediate materials of 

 assimilation. 



But how is the proper juice, which is thus so in- Anddis- 

 dispensable to the process of vegetation, conveyed Ihro^g 

 to the several parts or organs of the plant ? As the } 1 a t n t t he 

 sap in its ascent to the summit of the leaf is con- 

 ducted by an appropriate set of vessels, so also is 

 the proper juice in its descent to the extremity of 

 the root. One of the earliest and most satisfactory 

 experiments on this subject, at least as far as regards 

 the return of the proper juice through the leaf and 

 leaf-stalk, is that of Dr. Darwin, which was con- 

 ducted as follows : A stalk of the Euphorbia helis- 



