About the time when Tournefort was engaged in arranging his system of plants, and when Grew had completed his microscopical observations, John Ray was driven from his collegiate employments at Cambridge by differences of opinion with the ruling powers of his university. He sought and found consolation in the study of natural history, to which he was ardently attached, and for which his powers of observation, capacious mind, and extensive learning so highly qualified him. Profiting by the discoveries of Grew and other vegetable anatomists, in 1686 he published the first volume of his _Historia Plantarum_, in which are embodied all the facts connected with the structure and organs of plants, with an exposition of the philosophy of classification, the merits of which are better appreciated now than they were in his own days. Ray was careful to guard his readers against the supposition that classification was other than a means of identification. He argued that there was no line of demarcation in nature between one group or order, or even genus, and another, or that any system could be perfect. While he enumerated the true uses of classification, Ray also laid the foundations of the natural system, which has since been universally adopted by botanists. He separated flowerless from flowering plants, and he divided these again into Monocotyledonous and Dicotyledonous plants. Forty years after the publication of Tournefort’s system, and while Ray was yet pursuing his philosophical investigations, the Linnæan system appeared. This new mode of distributing vegetable species was hailed with admiration. Its author, Charles von Linnæus, reigned supreme and without a rival till the end of the Eighteenth Century, and even in our days his partisans are neither few nor powerless. In Germany, for instance, more than one botanical work of character has for foundation the system of Linnæus, and many school-gardens are arranged after his classification.