104 On the Anatomy of Fisgeinbles; intended to substantiate 



the earth is full ; the other tlrawinc; its Foundation tVo:ii the at- 

 mosphere, and composed of the narcotic principles, tannin, oils, 

 extractive matter, gums and resins, &c. Sec. Tims tliev are as 

 various in their effects as imhke in their appearance ; the one 

 tanning leather, t!ie other having no effect of this kind But 

 this confusion has arisen from the firs, where the turpentine is 

 apt to spread not a httle into the wood, and tluis mix with the 

 sap, which, in this case, loses a Httle. But its overrunning its pro- 

 per bounds is no reason for reckoniui.', the two juices the same : 

 the one is compounded in the leaves of the tree, the foundation 

 taken from the atmosphere ; the other proceeding from the 

 juices of the earth, and to be considered as the hquid of the 

 ground ratlier than the juices of the plant. 



I shall first show how the bark juice is formed. It is composed 

 in the pabulum of the leaves, to which the juices (taken by means 

 of the hairs from the atmosphere) constantly contrihvte ; and 

 when the pabulum is completed, the rest of the juices flow in 

 large vessels from the leaf-stem to the bark. Now this is what 

 Mr. Kniofit calls " the return of the sap." But there is not a 

 drop of sap in it, and his mistake arises from taking the muscles 

 for sap-vessels. However, when once this is proved a mistake, all 

 the fabric must fall with it That the muscles which run from 

 the wood to the leaves, and which are commonly called the spiral 

 wire, are incapable of carrying sap, is easily shown : two of them 

 are perfectlv witiiout aperture; and the middle one, though hol- 

 low, contains nothing but oil to humect and lubricate the spiral, 

 that it may not contract, and thus let nut (by continual agi- 

 tation) the most important part of tkeplant . 



The sap has but two ways of flowing up the tree : tiie first is 

 up the alburnum vessels, which continue to run up the tree for a 

 whole week or longer, twice in the year, and which is called the 

 barking time, because, in running in its place between the bark 

 and wood, it detaches one from the other, and bv separa ing al- 

 lows time for the sap to coagulate and form a new row of wood; 

 while the sap also pushing back the bark prepares a fresh row 

 of alburnum, allowing the wood-vessels to lengthen, and bv thus 

 increasing runs through the new wood. A large collection of 

 sap is always to be discovered at the bottom of the root at this 

 time, serving as a reservoir for the alburnum; which plainly shows 

 " that this ascension of the sap is managed by a different law 

 than the flowof the sap in the wood," since that has no reservoir 

 he low. 



The next manner of the flow of the sap is up the wood-vessels. 

 This is a constant rill, which is however much (juickened in the 

 morning or evening j but continues more or less throughout the 

 year. 



sir 



