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[42], 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[43]. 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[44] 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 therefore (p. 143) the swelling must be attributed "to some other cause than the stoppage of the sap in its return downwards," because the first gap in the bark should be sufficient to check the whole of the flowing sap[45]. He must in fact have seen that there is a redistribution of plastic material in each section of bark. We now for the moment leave the subject of transpiration and pass on to that of root-pressure on which Hales is equally illuminating. [Illustration: Figure from _Vegetable Staticks_ showing a vine with mercury gauges in place to demonstrate root-pressure.] His first experiment, _Vegetable Staticks_, p. 100, was with a vine to which he attached a vertical pipe made of three lengths of glass-tubing jointed together. His method is worth notice. He attached the stump to the manometer with a "stiff cement made of melted Beeswax and Turpentine, and bound it over with several folds of wet bladder and pack-thread." We cannot wonder that the making of water-tight connexions was a great difficulty, and we can sympathise with his belief that he could have got a column more than 21 feet high but for the leaking of the joints on several occasions. He notes the familiar fact that the vine-stump absorbed water before it began to extrude it.