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 58 transitions between the former and leafy branches. There is no reason to suppose, however, that our author was acquainted with the work of Albertus. Grew realised the nature of Bulbs, and points out that "the Strings only, are absolute Roots; the Bulb, actually containing those Parts, which springing up, make the Leaves or Body; and is, as it were, a Great Bud under ground."

Nehemiah Grew was interested in plant physiology, although the state of chemical and physical knowledge at the time did not allow of his advancing so far in this, as in the morphological side of the subject. His turn of mind, too, appears to have naturally led him to the study of form rather than that of function. As regards the absorption of water, his idea was simply that the roots sucked up water like a sponge, because the parenchyma was of a spongy nature. He supposed that the liquid was rendered purer by being strained through the skin, which, according to whether it was of a texture resembling brown paper, cotton, or leather, would produce a different effect upon any solution passing through it. His explanation of the ascent of the sap had really much in common with the "Kletterbewegung" theory propounded by Westermaier almost exactly two hundred years later. Grew argued that "considering to what height and plenty, the Sap sometimes ascends; it is not intelligible, how it should thus ascend, by virtue of any one Part of a Plant, alone; that is neither by virtue of the Parenchyma, nor by virtue of the Vessels, alone." He pointed out that the parenchyma might suck up a liquid for a short distance, and also the vessels, like "small Glass-Pipes immersed in Water, will give it an ascent for some Inches; yet there is a certain period, according to the bore of the Pipe, beyond which it will not rise." To account for the rise he supposes that the vessels and parenchyma work together, the turgidity of the surrounding parenchyma cells both compressing the vessels, and thus causing the liquid in them to ascend, and also actually forcing some of their own contents into them.