98 ACCOUNT OF SOME EXPERIMENTS ON THE 



I brought the under surface of the leaf into contact with it, by means of 

 a silk thread and a small wire adapted to its form and size. Having 

 retained the leaf in this position one minute, T removed it, and found the 

 surface of the glass covered with a strong dew, which had evidently 

 exhaled from the leaf. I again brought the leaf into contact with the 

 glass, and, at the end of half an hour, found so much water discharged 

 from the leaf, that it ran off the glass when held obliquely. 



I then inverted the position of the leaf, and placed its upper surface 

 in contact with the glass : not the slightest portion of moisture now 

 appeared, though the leaf was exposed to the full influence of the meridian 

 sun. These experiments were repeated on many different leaves ; and, 

 the result was, in every instance, precisely the same. It seems, there- 

 fore, that, in the vine, the perspiratory vessels are confined to the under 

 surface of the leaf ; and these, like the cutaneous lymphatics of the 

 animal economy, are probably capable of absorbing moisture, when the plant 

 is in a state to require it. The upper surface seems, from the position it 

 always assumes, either formed to absorb light, or to operate by the influ- 

 ence of that body : and if any thing exhale from it, it is probably vital air, 

 or some other permanently elastic fluid. It nevertheless appears evident, 

 in the experiments of Bonnet, that this surface of the leaves of many 

 plants, when detached from the tree, readily absorbs moisture. 



Selecting two young shoots of the vine, growing perpendicularly 

 against the back wall of my vinery, I bent them downwards, nearly 

 in a perpendicular line, and introduced their succulent ends, as layers, 

 into two pots, without wounding the stems, or depriving them of any 

 portion of their leaves. In this position, these shoots, which were about 

 four feet long, and sprang out of the principal stem, about three feet 

 from the ground, grew freely, and in the course of the summer reached 

 the top of the house. A s soon as their wood became sufficiently solid 

 to allow me to perform the operation with safety, I made two circular 

 incisions through the bark of the depending part of each shoot, at a 

 small distance from each other, near the surface of the mould in the 

 pots, and I wholly removed the bark between the incisions ; thus cutting 

 off all communication through the bark between the layers and the 

 parent stems. Had the subjects of this experiment now retained their 

 natural position, much new wood and bark would have been formed at 

 the upper lip of the wounds, and none at all at the lower, as I have 

 ascertained by frequent experiment. The case was now different : much 

 new bark and wood was generated on the lower lip of the wounds, 

 because uppermost by the inverted position of the branches ; and I have 



