256 PHILOSOPHICAL TRANSACTIONS. [aNNO I716. 



that is, the principal part of it, receives into it such juices of the earth as are 

 proper for it, and no other. Somewhat like a wick of cotton, which having 

 been impregnated with oil, will only admit oil into it. This provision being 

 made in the stomach of the plant, as I may call it, chiefly in the autumn 

 months, the tree is prepared for germination as soon as the earth is sufficiently 

 warmed, either by the sun's beams, or an artificial heat, such as horse-dung, 

 bran and water, or other such like ferments. These heats raise into vapour the 

 juices contained in the root, and by that means cause vegetation. 



Fig. 6, pi. 5, is part of the branch of an apple-tree, produced in May 1715, 

 and cut in April 17 l6. It was cut in the figure of a half-cylinder, the length 

 somewhat more than the diameter, which was about a quarter of an inch. This 

 being magnified with one of Campani's microscopes, discovers the following 

 parts, viz. 



1, 2, 3, 4, 5, 6, 7, are capillary vessels, which run longitudinally through 

 the branch, in the ligneous part, which was made in the year 1715. Through 

 these tubes the steam rises from the root ; the strength of which is well ex- 

 plained by Capt. Savory's engine for raising water by fire. From a to b we may 

 view vessels of the same sort, produced at the same time. 8, Q are vessels of 

 the same use with the former, now forming for the use of the year 1 7 J 6. By 

 this means the diameter of the branch is increased, and additional nourishment 

 suffered to pass into those buds which are to make new branches. These are 

 made out of the 4th or innermost bark, marked cc. 



The mouths of the capillary tubes of the years 1715 and 171 6, are d, e. 

 The vapour which rises from the root, is continued in these vessels, to the ex- 

 tremities of the branches ; where it meets with parts (not here represented), 

 resembling glands ; which glands, if we may so call them, are likewise found at 

 every knot or joint. At these places, the vapour coming near the air is con- 

 densed, and returns between the barks, by means of its own weight, down 

 p, G, H, leaving in each- bark marked i, k, l, such juices as each of them 

 naturally is inclining to separate from it ; till at last, the more oily part passing 

 to the root, may lengthen its fibres, as icicles are lengthened; and by its oleous 

 particles, preserve them from rotting by the wet. The parts which compose 

 the several barks, are parenchymous or spongy. 



The first marked m, is of a closer texture than the second n, and the second 

 closer than the third o, and so on till these parenchymous parts are interwoven 

 with the longitudinal wood-vessels, where they are somewhat constrained, till 

 they come to make the pith, marked p. Then they are much larger than in 

 any other part of the tree ; and by what I have observed, seem to contain a 

 more finished juice than the rest, and may well enough be stiled the medulla. 



