Page:An introduction to physiological and systematical botany (1st edition).djvu/43

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or perhaps from mere water and air. The most different and discordant fluids, separated only by the finest film or membrane, are, as we have already observed, kept perfectly distinct, while life remains; but no sooner does the vital principle depart, than secretion, as well as the due preservation of what has been secreted, are both at an end, and the principle of dissolution reigns absolute.

Before we can examine the physiology of vegetables, it is necessary to acquire some idea of their structure.

Much light has been thrown upon the general texture of Vegetables by the microscopic figures of Grew, Malpighi and others, repeated by Dr. Thornton in his Illustration of the Linnaean System, but more especially by the recent observations and highly magnified dissections of M. Mirbel. See his Table of Vegetable Anatomy in the work already mentioned. From preceding writers we had learned the general tubular or vascular structure of the vegetable body, and the existence of some peculiar spirally-coated vessels in many plants. On these slender