This extraordinary work made its nu slowly. At the time of its appearance the greater part of botanists were full of zeal and prejudice in favour of the sexual system of Linnaeus; an idea prevailed that botany was merely the art of distinguishing one thing from smother; and moreover the political state of Europe was most unfavourable to scientific investigation!. As tranquillity was restored iu France the work of Jussieu began to be studied, and being studied it soon became the text-book of all the botanists of reputation in that country. But in the other nations of Europe it was otherwise. In England, when Dr. Robert Brown published his ' Prodromns Flom Hollandim,' in 1810, upon the system of Jussieu, there probably were not more than two or three other botanists in this country who could understand or make use of it; Elul it was not till after the year 1820 that it became much known among us.
In his Genera Plantarum,' Jussieu divided the vegetable kingdom into classes, subclasses, orders, and genera, not according to certain arbitrary distinctions, but by taking into consideration all the circum stances which he was acquainted with in their manner of growth and degree of development. Those which he regarded as the least perfectly organised species he stationed at the one end of his system, and, proceeding upon the principle of continually grouping together those plants which resemble each other more than they resemble any thing else, he gradually arrived at the highest forms of vegetable life through a long series of intermediate gradations. In determining the relative dignity of his orders, he assumed that those species are least perfectly organised which have no cotyledon or rudimentary leaf iu their embryo ; that next in degree, but higher than these, are such as have one cotyledon ; and that highest of all are those whose seeds have two cotyledons : hence his classes Acotyledons, Monocotyledons, and Dicotyledons. In arriving at this conclusion he was justified by the fact that to the highest class belong the lofty trees of the forest, with all their intricate apparatus of trunks, and arms, and branches; to the middle the simple-stemmed palms, lilies, and grasses ; and to the lowest such forms of vegetation as Fungi, lichens, and sea-weeds.
In determining the subordination of the genera assembled under each of these classes Jussieu was influenced by other considerations. He regarded those dicotyledonous genera which have no corolla as lower than such as possess that organ, and among those which have it the adhesion of the parts of the corolla into a tube was looked upon as an indication of a structure inferior to the total separation of the petals : this gave him for his great dicotyledonous class the subclasses Apetala, Monopetalce, and Polypetalts. In addition to which he formed another subclass, called Melina irregulars*, out of such dicotyledonous plants as have the sexes separated, which he considered an irregularity of organisation. As a lest method of division Jussieu applied to Monocotyledons and all the subclasses of Dicotyledons a principle of analysis dependent upon the situation of the stamens, calling them hypogynous' if the stamens originate clear of both calyx and ovary; perigynous ' if they grow from the calyx or corolla ; and epigynous ' if their apparent origin is in the apex of the ovary. There seems to have been no other reason for this than that such a "triplex staminis situ*" was found to exist. The result of all these distinctions was the following scheme, under which were arranged all the natural orders known to the author :— In the state of science when this system was promulgated its excellence was most remarkable. Its faults are the artificial nature of all the divisions except those which are primary, the difficulty in many cams of determining to which of them a given plant belongs, and the nnmerous exceptions to which they are all subject, which may be owing to their being mere structural and not physiological distinctions.
They have accordingly been much criticised, especially of late years, and every original writer attempts to improve them, with various success. But, to use the words of his eon, to whose sentiments it is Impossible for any botanist to refuse his assent, "What is it that is most admired in this work l not so much the systematical key, which has been so often attacked and abandoned by modern writers, as the admirable sagacity which regulated all the details. It is the neatness of the characters, the happy employment of such as had been pre vionaly neglected, and the correct estimate of their value, the pro digality with which notes full of deep knowledge and fruitful in new ideas are dispersed throughout the work, the endless questions and doubts, which show how much the author had meditated upon his subject, and that he was among the first to regret the sacrifices he was compelled to make to the necessity of a systematical arrangement; and finally, that instinct, so true to natural affinities, which so often made him suspect the truth when he could not establish it." No doubt Jussieu was largely indebted to our countryman Ray, r whose name however does not appear among his introductory remarks; no doubt he was also assisted most essentially by Tournefort, Linnwus, and other systematical writers ; but we are not on that account to withhold from him one particle of that merit which his countrymen eagerly claim for him. Ray could not apply his own principles; Touruefort and LinnNns were mere system-makers, who did not understand the principles of philosophical classification ; but Jussieu had the philosophy of the one, the systematical abilities of the others, and the peculiar skill of combining them into a consistent whole. His Genera Plantarum' is now obsolete : for what has since been done towards giving a more philosophic character to the study of systematic botany we refer to the article BOTANY, in the NATURAL HISTORY DIVISION of the ENOLISTI CYCLOPEDIA.
In 1779, when the Genera Plantarum' was published, the political state of France, which put an end to peaceful occupations, and turned the public from all thoughts of botany, disturbed the tranquil tenor of the course of Jussieu, and compelled him to mingle in the busy scenes of public life. In 1790 he was named member of the munici pality of Paris, and in this character was charged with the direction of the hospitals and charities of that city, which he continued to exercise till 1792. In 1793 the Jardin du Roi was re-organised under the new name of Jardin des Plantes; all the persons charged with the duty of public instruction were elevated to the rank of professors, and De Jussieu, who had been previously Botanical Demonstrator, became Professor of Rural Botany. He afterwards became director and treasurer of the Museum of Natural History, and recommenced, in 1802, his botanical writings, chiefly in the form of memoirs upon his own natural orders of plants. These, amounting in number to fifteen, were continued in the Annales du Museum' till 1820, after which time De Jussieu became dead to science. He was then seventy-two, with a sight so feeble that it might almost have been called blindness, and he was no longer able to do more than profit by the observations of others. Nevertheless, he employed himself between his eighty-third and eighty-eighth year in dictating a new edition of his Introductio in Historians Plantarum.' This work was published after his death ; it is written in elegant Latin, and is a remarkable proof of the vigour of his Intellect even at this advanced age. He appears to have been much loved by his family and greatly respected by his friends. Hie amenity of character was such that he was never in any one of his writings betrayed into a single word of harshness towards his con temporaries. He died, after a short illness, on the 15th of September 1836.