SECT. XXIII. THE SAP. 45? 



SECTION XXIII. 



The Sap. 



IF the branch of a Vine is cut asunder early in How ex- 

 the spring before the leaves have begun to expand, 

 a clear and colourless fluid will issue from the 

 wound, which gardeners denominate the tears of 

 the Vine. It is merely, however, the ascending sap, 

 and may be procured from almost any other plant 

 by the same or similar means, and at the same sea- 

 son ; but particularly from the Maple, Birch, and 

 Walnut-tree, by means of boring a hole in the 

 trunk. It issues chiefly from the porous and 'mixed 

 tubes of the alburnum ; though sometimes it does 

 not flow freely till the bore is carried to the centre.* 

 A small branch of a Vine has been known to yield 

 from twelve to sixteen ounces, in the space of 

 twenty-four hours. A Maple-tree of moderate size 

 yields about 200 pints in a season, as has been al- 

 ready stated ; and a Birch-tree has been known to 

 yield in the course of the bleeding season, a quantity 

 equal to its own weight. 



The taste of this .fluid is generally insipid ; but Properties, 

 sometimes it is slightly saline, and sometimes agree- 

 ably sweet, as in the case of the Birch-tree. If it 



* Exper. par Coulomb, Jour, de Phys. vol. xlix. p. 3p2. 



