4(3O COMPOUND PRODUCTS. CHAP. I. 



and it is well known that the sap of the American 

 Maple-tree yields a considerable quantity of sugar. 



SECTION XXIV. 



The Proper Juice. 



How dis- WHEN the sap has received its last degree of ela- 

 fron" the boration from the different organs through which it 

 sap ' has to pass, it is converted into a peculiar fluid 

 called the Proper Juice. This fluid may be dis- 

 tinguished from the sap by means of its colour, 

 which is generally green, as in Periwinkle ; or red, 

 as in Logwood ; or white, as in Spurge ; or yellow, 

 as in Celandine ; from the two last of which it may 

 readily be obtained by breaking the stem asunder, 

 as it will then exude from the fracture. Its prin- 

 cipal seat is in the bark, where it occupies the simple 

 tubes ; but sometimes it is situated between the 

 bark and wood, as in the Juniper-tree ; or in the 

 leaf, as in the greater part of herbs ; or it is dif- 

 fused throughout the whole plant, as in the Fir and 

 Hemlock ; in which case, either the proper juice 

 mixes with the sap, or the vessels containing it have 

 ramifications so fine as to be altogether impercepti- 

 ble. It is not however the same in all plants, nor 

 even in the different parts of the same plant. In the 

 Cherry-tree it is mucilaginous; in the Pine it is 

 resinous ; in Spurge and Celandine it is caustic, 

 though resembling in appearance an emulsion. In 



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