The physiology of the circulation in plants : in the lower animals, and in man : being a course of lectures delivered at surgeons' hall to the president, fellows, etcof the Royal college of surgeons of Edinburgh, in the summer of 1872 . at trees havea season of activity and a season of repose ; that they increase inan upward direction by means of shoots, in a downward directionby means of roots, and laterally by In other words, theyincrease in every direction; and this holds true of growing animalsas well as growing plants. The shoots, by their upward growth, tendto draw up the sap;
The physiology of the circulation in plants : in the lower animals, and in man : being a course of lectures delivered at surgeons' hall to the president, fellows, etcof the Royal college of surgeons of Edinburgh, in the summer of 1872 . at trees havea season of activity and a season of repose ; that they increase inan upward direction by means of shoots, in a downward directionby means of roots, and laterally by In other words, theyincrease in every direction; and this holds true of growing animalsas well as growing plants. The shoots, by their upward growth, tendto draw up the sap; the roots, by their downward growth, to drawit down; and the branches, by their lateral growth, to draw ittransversely. Here, then, are the materials for an interrupted ordisjointed circulation with a certain degree of oneness about is a principal factor in the process. The idea of a plantor tree increasing in an upward and downward direction andlaterally at one and the same time, is consistent with fact. Whena seed grows, it extends itself into the ground and into the air; ,it spreads from a centre in an upward and outward direction, andin a downward and outward (Figs. 1, 2, and 3.) Fig. 2. Fig. Fig. 1.— A seedling dicotyledonous plant with an ascending and a descending axis.—Henfrey. Fig. 2.—• Pandanus odoratissimus, the screw-pine, with adventitious roots supporting thetrunk/—Henfrey. Fig. 3.—Rhizophora mangle, the mangrove-tree, supported as it were upon piles by itsnumerous roots, which raise up the stem. The plant grows at the muddy mouths of riversin warm climates.—Balfour. If, bearing this fact in mind, you imagine that as the tree grows,the central point from which it had its being moves upwards (itmust do this if it is to maintain its central position with referenceto the tree as a whole), then we are forced to conclude that the ment may be—1st, from the place of formation to that of consumption ; or, 2d,to the stem, c
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