66 TEANSITION OF INORGANIC INTO ORGANIC MATTER. 



parts, the organic matters dissolved in the fluid appear to undergo 

 important modifications; for in the sap substances are detected 

 which could not have existed in the water which moistened the soil. 

 During its ascent the sap increases in density, as was ascertained 

 by Mr. Knight, according to whom, the sap of an acer platanoides^ 

 taken at the level of the ground, has a density of 1.004 ; at 67 feet 

 above it this density becomes 1.008, and at 13 feet, 1.012. From 

 this Mr. Knight concluded that the sap took up nutritive matter 

 deposited in the vegetable tissues which it traversed in its ascent.* 

 We have already seen that the sap, after being elaborated in the 

 green parts of trees, takes a route the reverse of that which it fol- 

 lowed at first, and we therefore spoke of this modified sap as the 

 descending sap. It is very possible that in Knight's observations 

 the liquid examined was a mixture of the two saps. 



We should not be over hasty in concluding that the action of the 

 two species of sap was exerted separately in promoting the develop- 

 ment of the plant ; it is very probable, as Dutrochet thinks, that the 

 modified sap, by insinuating itself into the permeable tissue of the 

 vegetable, is continually mixed with the ascending sap, in order to 

 concur in promoting the growth of the buds.f The difficulty of 

 obtaining each particular sap separately, if such a separation is reallv 

 possible, prevents the analytical conclusions we have from possess- 

 ing all the accuracy that seems desirable. 



Vauquelin has studied the sap of the birch- tree, of the hornbeam, 

 of the beech, of the chestnut, and of the elm. 



The sap of the hornbeam {Carpinus sylvestris) was obtained in 

 the months of April and May. At this period it is colorless and 

 clear as water ; its taste is slightly saccharine ; its odor resembles 

 that of whey ; it reddens turnsole paper. The sap of this tree 

 contains water in very large quantity, sugar, extractive matter,^ 

 and free acetic acid, acetate of lime and acetate of potash, in very 

 small quantity. 



This sap left to itself presents in succession all the phenomena of 

 the vinous and then of the acetous fermentation.^ 



The sap of the birch-tree reddens turnsole intensely ; it is color- 

 less, and has a sweet taste. The water which forms the greater 

 part of it, holds in solution sugar, extractive matter, acetate of 

 lime, acetate of alumina, and acetate of potash. 



Whea properly concentrated by evaporation, it ferments on the 

 addition of yeast, and then yields alcohol on distillation. The pre- 

 sence of the acetate of alumina may appear extraordinary in this 

 sap, for this reason, that alumina has not yet been discovered in the 

 ashes of the birch-tree. 



Sap of the beech, {Fagus sylvestris ) The analysis was made in 

 Marcli and April. Tlie color of the sap was a tawny red : it had 

 the taste of an infusion of tanner's bark : it reddened turnsole slignt- 



* Decandolle, Physiologic, t. i. p. 204. 



t Dutrochet, sur la Structure, &c. p. 36 



t Probably azotized. 



^ Vauquelin, Annales de Chunie, t. xxxi. p. 90, lire wMm. 



