Page:Philosophical Transactions - Volume 004.djvu/75



Birch-trees the Sap issues out of the least twiggs of Branches, and fibres of Roots, in proportion to their bigness.

2. In all Trees the Gravity promotes the Bleeding; so that from a Branch or Root, that bendes downward, there will issue a great deal more Sap, than from another of the same bigness in a more erect posture.

3. Branches and Young trees cut quite off when they are full of Sap, and held perpendicularly, will bleed; as we experimented in Willow, Birch, and Sycamore: And if you cutt off their tops, and invert them, they will bleed also at the little ends. Hence one may conjecture, that the narrowness of the pores is not the sole cause of the Ascent of the Sap; for, Water that hath ascended in the little glass-pipes, will not fall out againe by its own gravity, if the pipes be taken our of the water.

4. Roots of Birch and Sycamore cut asunder will bleed both ways, that is, from that part remaining to the Tree, and from the part separated; but a great deal faster from the part remaining to the Tree. But in a cold snowy day the Root of one Sycamore, we had bared, bled faster from the part separated, and ten times faster than it did in warm weather before.

5. In Birches the Sap does not issue out of the Barke, be it never so thick, bus as soone as ever you have cutt the Barke quite through, then it first begins to bleed.

6. The Bark being quite pared off above an hands breadth round, about severall Birches, did much abate the Bleeding of the Trees above the bared places, but did non quite stop it.

7. The Sap doth not only ascend between Bark and Tree, Rh