The Third Era.—About the middle of the 17th century this instru ment was first employed in the examination of the elementary organs of plants, about which nothing had been previously learned since the time of Theophrastus. The discovery of spiral vessels by Heushaw in 1661, the examination of the cellular tissue by Hook at a somewhat later date, at once excited the attention of observers and led at nearly the same time to the appearance of two works upon vegetable anatomy, which at once so nearly exhausted the subject that it can scarcely be said to have again advanced till the beginning of the present ceutury. Grew and Malpighi, the writers here adverted to, but more especially the former, combined with rare powers of. observation a degree of patience which few men have ever 'possessed. They each examined the anatomy of vegetation in its minutest details, the former princi pally in the abstract, the latter more comparatively with the animal kingdom. Various forms of cellular tissue, intercellular passages, spiral vessels, woody tubes, ducts, the nature of hairs, the true struc ture of wood, were made at once familiar to the botauist; the real nature of sexes in plants was demonstrated; and it is quits, surprising to look back on those days front the present high ground on which botany has taken its stand, and to see how little the views of Grew at least have subsequently required correction. From him physiological botany properly speaking took its origin. Clear and distinct ideas of the true causes of vegetable phenomena gradually arose out of a consideration of the physical properties of the minute parts through whose combined action they are brought about ; and a solid founda tion was laid for the theories of vegetation which subsequent botanists have propounded: to Grew 'Impels° be ascribed the honour of having first pointed out the important difference between seeds with one cotyledon and those with two, and of having thus been the discoverer of the two great natural classes into which the flowering part of the vegetable kingdom is now divided. Grew however was no systematist; it was reserved for another Englishman to. discover the true principles of classification, and thus to commence The Fourth Era.—John Ray, a man of capacious mind, of singular powers of observation and of extensive learning, driven from his collegiate employments by the infamous commands of a profligate prince, sought consolation in the study of natural history, to which be had been attached from his youth. Botany lie found was fast settling back into the chaos of the middle ages, partly beneath the weight of undigested materials, but more from the want of some fixed principles by which the knowledge of the day should be methodised. Profiting by the discoveries of Grew and the other vegetable anato mists, to which ho added a great store of original observation, he in his ' Historia Plantarum,' the first volume of which appeared iu 1686, embodied in one connected series all the facts that had been collected concerning the structure and functions of plants : to these lie added an exposition of what lie considered the philosophy of chuisification, as indicated partly by human reason and partly by experience; and from the whole he deduced a classification which is unquestionably the basis of that which, under the name of the system of Jussieu, is everywhere recognised at the present day. For proofs of this we refer to the memoir of RAY in the Hire., Bloc., &c. DIVISION. We will only observe here that he separated flowering from flowerless plants; that he divided the former into monocotyledons and dicotyledons, and that under these three heads he arranged a considerable number of groups, partly his own, partly taken from Lobel and others; which are substantially the same as what are received by botanists of the present day under the name of natural orders. It is singular enough that the merits of this arrangement of John Ray should have been so little appreciated by his contemporaries and immediate successors as to have been but little adopted ; and that instead of endeavouring to correct its errors and to remove its imperfections, botanists occupied themselves for several succeeding years in attempts at discovering other systems, the greater part of which were abandoned almost as soon as they were made known. Rivinus, Magnol, Tournefort, and Linnaeus were the most celebrated of these writers; but the two last alone have had any permanent reputation. Tournefort, who for a long time stood at the head of the French school of botany, proposed in 1694 a method of arrangement, in its principles entirely artificial, but which in some cases was accidentally in accordance with natural affinities. It was founded chiefly upon differences in the corolla, without the slightest reference to physiological peculiarities ; and is now forgotten, except in consequence of its having furnished some useful ideas to Jussieu, as will be hereafter shown.
The Fifth Era.—Linnaeus was a genius of a different and a higher order. Educated in the severe school of adversity, accustomed from his earliest youth to estimate higher than all other things verbal accu racy and a logical precision, which are often most seductive when least applicable; endowed by nature with a most brilliant uuderstanding, and capable, from constitutional strength, of any fatigue either of mind or body, this extraordinary man was destined to produce a revo lution in botany, among other branches of natural history, which in some respects advanced and in others retarded its progress far mere than the acts of any one who bad preceded him. He found the
phraseology bad, and he improved it ; the nomenclature was awkward and inconvenient, he simplified it ; the distinctions of genera and species, however much the former had been improved by Tournefort, were vague and too often empirical—he defined them with an appa rent rigour which the world thought admirable, but which nature spurned ; he found the classifications of his day ao vague and uncer tain that no two persons were agreed as to their value, and for them he substituted a scheme of the most specious aspect, in which all things seemed as clearly circumscribed by rule and line as the fields in the map of an estate ; he fancied he had gained the mastery over nature, that he had discovered a mighty spell that would bind her down to be dissected and anatomised, and the world believed him ; in short, he seized upon all the wardrobe of creation, and his followers never doubted that the bodiless puppets which he set in action were really the divine soul and essence of the organic world. Such was Linnaeus, the mighty spirit of his day. Let us do this great man that justice which exaggeration on the one hand and detraction on the other have too often refused to him, and let us view his character soberly and without prejudice. We shall then admit that no natu ralist has ever been his superior ; and that he richly merited that high station in science which he held for so many years. His verbal accu racy, upon which his fame greatly depends, together with the remark able terseness of his technical language, reduced the crude matter that was stored up in the folios of his predecessors into a form that was accessible to all men. He separated with singular skill the important from the unimportant in their descriptions. He arrayed their endless synonyms with a patience and lucid order that were quite inimitable. By requiring all species to be capable of a rigorous definition not exceeding twelve words, he purified botany of the endless varieties of the gardeners and herbalists; by applying the same strict principles to genera, and reducing every character to its differential terms, he got rid of all the cumbrous descriptions of the old writers. Finally, by the invention of an artificial system, every division of which was defined in the moat rigorous manner, he was able so to classify all the materials thus purified and simplified that it seemed as if every one could become a botanist without more previous study than would be required to learn how to discover words in a dictionary. Add to all this the liveliness of his imagination, the skill with which he applied his botanical knowledge to practical objects, and the ingenuity he showed in turning to the purposes of his classification the newly discovered sexes of plants, and we shall at once comprehend what it was that exalted Linnaeus so far above his contemporaries. But great as the impulse undoubtedly was which Linnaeus gave to botany, there were vices in his principles which although overlooked during his life have subsequently been productive of infinite evil. There is no such thing as a rigorous definition in natural history ; this fact Ray had demonstrated to arise out of the very nature of things ; and conse quently the short phrases by which species and genera were charac terised by Linnaeus were found equally applicable to many other plants besides those for which they were intended : hence arose a new source of confusion, inferior only to that which it was intended to correct. Differential characters, which would bo invaluable if we had all nature before us, were found in practice to lead to incessant errors, so soon as some new species was introduced into the calculation : they also laboured under the great fault of conveying uo idea whatever of the general nature of the plants to which they related : thus the Portu guese botanist Loureiro, who attempted to determine the plants of China by the systematic writings of Linnaeus, fell into the singular error that the hydrangea was a primrose. With regard to his artificial system of classification, it was found that it looked better in the closet than in the field ; that the neatness and accuracy of the distinctions upon which it was divided into groups existed only upon paper, and that exceptions without end encumbered it at every turn. This, which is perhaps inseparable from all systematic arrangements, would not have been felt as so great an evil if there had been any secondary characters by which the primary ones could be checked, or if the system had really led with all its difficulties to a knowledge of things. But it was impossible not to perceive that it led in reality to little more than a knowledge of names, and that it could be looked upon as nothing beyond an index of genera and species.