water. There are, however, pitfalls in this result of which Hales was unaware, and perhaps the chief interest to us now is that he considered the imbibition of the peas[1] to be the same order of phenomenon as the absorption of water by a cut branch—notwithstanding the fact that he knew[2] the absorption to depend largely on the leaves. It may be noticed that Sachs with his imbibitional view of water-transport may be counted a follower of Hales.
In order to ascertain "whether there was any lateral communication of the sap and sap vessels, as there is of blood in animals," Hales (p. 121) made the experiment which has been repeated in modern laboratories[3], i.e. cutting a "gap to the pith" and another opposite to it and a few inches above. This he did on an oak branch six feet long whose basal end was placed in water. The branch continued to "perspire" for two days, but gave off only about half the amount of water transpired by a normal branch[4]. He does not trouble himself about this difference, being satisfied of "great quantities of liquor having passed laterally by the gap."
He is interested in the fact of lateral transmission in connexion with the experiment of the suspended tree (Fig. 24, p. 126), which is dependent on the neighbours to which it is grafted for its water supply. This seems to be one of the results that convinced him that there is a distribution of food material which cannot be described as circulation of sap in the sense that was then in vogue.
Hales (p. 143) was one of the first[5] to make the well-known experiment—the removal of a ring of bark, with the result that the edge of bark nearest the base of the branch swells and thickens in a characteristic manner. He points out that if a number of rings are made one above the other, the swelling is seen at the lower edge of each isolated piece of bark, and
- ↑ The method by which Hales proposed to record the depth of the sea is a variant of this apparatus.
- ↑ Vegetable Staticks, p. 92.
- ↑ According to Sachs (Geschichte, p. 509) Ray employed this method.
- ↑ Other facts show that the "gapped" branches did not behave quite normally.
- ↑ He refers (p. 141) to what is in principle the same experiment (see Fig. 27) as due to Mr Brotherton, and published in the Abridgment of the Phil. Trans. II. p. 708.
