THE FLUID COMPONENTS OF PLANTS. 243 



the transpiration of the plant, throwing off a large pro- 

 portion of the watery part of the matter taken up from 

 the soil. Such are the sensible qualities of the sap ; 

 its chemical properties and composition are discover- 

 ed by tests, and analysis by heat. 



According to Vauquelin, the sap of the Elm (Ul- 

 mus campestris), collected towards the end of April, 

 the beginning and the end of May, in 1039 parts 

 consisted of 1027.904 of water and volatile matter ; 

 9.240 of acetate of potash ; 1.060 of vegetable mat- 

 ter ; and 0.796 of carbonate of lime. The second 

 analysis of the sap collected at the beginning of May 

 afforded a greater proportion of vegetable matter, less 

 acetate of potash, and also less carbonate of lime ; and 

 in the third anal) sis of that collected at the end of 

 May, the quantity of the acetate of potash was still 

 more diminished, and also that of the carbonate of 

 lime. In all he found slight traces of sulphate and of 

 muriate of potash. From two different analyses of 

 the sap of the Beech (Fagus sy'vatka), procured also 

 at different periods of the same season, he obtained 

 water, acetate of lime, free acetic acid, gallic acid, and 

 tanin, with some vegetable extractive and mucous 

 matter. In the same manner he examined the sap of 

 the common Hornbeam (Carpinus Betulus), collect- 

 ed in March and April, and found in it, acetate of 

 of potash, acetate of lime, sugar, mucilage, vegetable 

 extract, and water. In the sap of the common Birch 

 (Betula alba), be found acetate of lime, acetate of 

 potash, acetate of alumina, sugar, vegetable extract, 

 and water. In all the specimens thus analyzed the 

 quantity of vegetable matter was found to be greater 

 in the sap drawn late in the season, than in that col- 

 lected at an earlier period of it. 



The modifications which take place in the roots of 

 plants, throw considerable obstacles in the way of ob- 



