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CHAPTER VIII.
OF THE SAP-VESSELS, AND COURSE OF THE SAP; WITH MR. KNIGHT'S THEORY OF VEGETATION.
Much contrariety of opinion has existed among physiologists concerning the vascular system of plants, and the nature of the propulsion of the sap through their stems and branches. Indeed it is a subject upon which, till lately, very erroneous ideas have prevailed.
That the whole vegetable body is an assemblage of tubes and vessels is evident to the most careless observer; and those who are conversant with the microscope, and books relating to it, have frequent opportunities of observing how curiously these vessels are arranged, and how different species of plants,
