12. That the sap- does circulate appears farther from 

 hence, that the graft will either corrupt or heal the 

 stock. Nay, it changes the very way of the growing 

 of the root, which it could not do but by sending down 

 its sap thither. Crab-stocks grafted with fruit, which 

 the soil does not like, will canker, not only in the 

 graft, but the stock also ; but graft them Rgain with 

 fruit it does like, and it will quickly heal. Farther; 

 graft twenty young pear-stocks with one sort of pear, 

 and twenty with another. The roots of one sort will 

 grow all alike, and so will those of the other. Yet 

 ever-greens grafted on trees which drop their leaves, as 

 the ever-green oak of Virginia upon the common Eng- 

 lish oak, hold their leaves all the winter. Does not 

 this shew that the juices circulate in winter as well aa^ 

 summer, even in the plants which drop their leaves? \^ 

 Otherwise those grafted on them must soon die. 



It seems that the sap does not rise by the pith ; be- 

 cause some large trees are without that part, and yet 

 continue to put forth branches. Indeed no pith is 

 found in those branches of a tree, which exceed two 

 or three years growth. And the pith which is in a 

 branch of this year, is distributed into those bought 

 whleh are formed the next season. 



Many believe the tree does not receive its nourish- 

 ment by the bark ; because trees that have lost that 

 part, continue to grow. But they suppose a tree has 

 but one bark, whereas every branch has four distinct 

 coverings. The two outermost of these may be taken 

 from a tree without much damage ; but if the two others 

 be taken off, it will infallibly kill the tree. 



Some afiirm that the sap neither rises nor falls in the 

 woody part of the tree, because when a branch is cut^ 

 they cannot discern any sap issue out of it. Certainly 

 they cannot; because those tubes are not large enough 

 to receive any thing more gross than vapour. The root 

 receives chiefly in autumn its proper juices, which the 

 warmth in spring raises into a vapour, that gradually 

 ascends through those fine tubes, and by that means 

 causes vegetation. 



