If we notice in the above table how the Phanerogams are separated into classes, it strikes us that the triple division into hypogynous, perigynous, and epigynous is repeated no less than four times; this shows that Jussieu had mistaken ideas of the value of these marks for classification, whereas the recurrence of them so often should of itself have suggested a doubt on this point. To judge of his system more exactly we must here give his series of the families, which he had already raised to the number of a hundred.

Jussieu’s division of the Cryptogams and Monocotyledons offers much that is satisfactory, if we put the position of the Naiades out of sight. The grouping of the Dicotyledons on the contrary is to a great extent unsuccessful, chiefly owing to the too great importance which he attached to the insertion of the parts of the flowers, that is, to the hypogynous, perigynous, and epigynous arrangement. It is in this grouping of families into classes that the weak side of the system lies; it is utterly artificial, and the task of his successors has been to arrange the families of the Phanerogams, which were most of them well-established, and especially those of the Dicotyledons, in larger natural groups. But this could not be effected, till morphology opened new points of view for systematic botany; Jussieu, as has been already remarked, accepted Linnaeus’ views of the morphology of the organs of fructification in Phanerogams, though he introduced many improvements in details. He laid greater stress on the number and relative positions of the different parts of the flower; attention to their insertion on the flowering axis, which he designated as hypogynous, perigynous, and epigynous, would have been a great step in advance, if he had not overrated its systematic value. The morphology of the fruit is very superficial in Jussieu; even the designation of dry indehiscent fruits as naked seeds recurs in his definitions, though as it happens this misconception does not cause any great disturbance. How inexact was his investigation of the organs of fructification, when they were somewhat small and obscure, is best shown by the fact that the Naiades, which are made to include Hippuris, Chara, and Callitriche, appear among the Acotyledons, and that Lemna and the Cycads are placed with the Ferns.

Jussieu explained the dictum, ‘Natura non facit saltus,’ to mean that the whole body of plants in its natural arrangement must exhibit a lineal series ascending from the most imperfect to the highest forms; but he does not say whether Linnaeus’ comparison of the natural system to a geographical map, the countries in which answer to orders and classes, is also admissible.

His theoretical observations on the value to be given to certain marks in a systematic point of view are not attractive, and for the most part not very correct; he speaks as though some marks must have a more extensive, others a less extensive value; the perception of the fact, so far as it is true, rests entirely upon induction; that is, after the natural affinities have been already recognised to a certain extent, it becomes apparent that certain marks remain constant in larger or smaller groups; the systematist can now go on to try whether such constant marks occur in other plants also, which he had hitherto assigned to other groups, and thus put it to the test whether those marks may not be accompanied by others, which would serve to establish the affinities; that Jussieu did so proceed in defining his families admits of no doubt, but he was not himself thoroughly conscious of the fact; at all events, he did not extend this mode of proceeding, the seeking after leading marks, to the establishing of larger groups or classes, for these he founded on predetermined principles.

Jussieu’s labours as a systematist were not confined to the publication of his ‘Genera Plantarum’; on the contrary, his most fruitful researches began after 1802, and were continued to the year 1820, and their results appeared in a long series of monographs on different families in the Mémoires du Museum. He felt with De Candolle, Robert Brown, and later systematists, that the perfecting of the natural system depended mainly on the careful establishing and defining of families. His efforts received a new impulse from the work of a German writer, whose first volume had appeared in 1788, a year therefore before the ‘Genera Plantarum,’ a second following it in 1791, and a supplementary volume in 1805.

This work was Joseph Gärtner’s[36] ‘De fructibus et seminibus plantarum,’ in which the fruits and seeds of more than a thousand species are described and carefully figured. But almost more important than these numerous descriptions, though they offered rich material to the professed systematists, were the introductions to the first two volumes, and especially to those of 1788. They contain valuable reflections on sexuality in plants,—a subject which had remained in the condition in which it was left by Camerarius (1694) till it was greatly developed by Koelreuter after 1761, and had since then been little studied,—and an account of the morphology of fruits and seeds, the knowledge of which had gone back rather than advanced since the days of Malpighi and Grew. Gärtner was well qualified for this work by his unparalleled knowledge of the forms of fruits, and still more by the character of his mind. Free from Linnaeus’ scholastic bias, he addressed himself to the examination of the most difficult organs of plants with as great freedom from prepossessions as exact acquaintance with the writings of others; he gives us the impression of a modern man of science more than any other botanist of the 18th century, with the exception of Koelreuter. He knew how to communicate with clearness of language and perspicuity of arrangement whatever he gathered of general importance from each investigation. Though it is easy to see that the founding of the natural system was ever before his mind as the final object of his protracted labours, he was in no eager haste to reach it; he contented himself with arranging his fruits, saying expressly that the natural system would never be founded by these means alone, though the exact knowledge of fruits and seeds supplied the most important means for decision. Thus his great work was at once an inexhaustible mine of single well-ascertained facts, and a guide to the morphology of the organs of fructification and to its application to systematic botany. The imperfections, which are to be found even in this work, are due to the circumstances of the time; in spite of Schmeidel’s and Hedwig’s researches into the Mosses there was still the old obscurity with regard to the organs of propagation in the Cryptogams, and this rendered a right definition of the ideas, seed and fruit, extremely difficult. But Gärtner made one great step in advance on this very point when he showed that the spores of the Cryptogams were essentially different from the seeds of Phanerogams, with which they had been hitherto compared, because they contain no embryo; he called them therefore not seeds, but gemmae. The second great hindrance to a true conception of certain characters in fruits and seeds on the part of Gärtner was the entire ignorance of the history of development which then reigned; yet even here we see an advance, if only a small one, made by him in his repeatedly going back to the young state for a more correct idea of the organs.

Above all, Gärtner put an end to the blunder of regarding dry indehiscent fruits as naked seeds, by rightly defining the pericarp as in all cases the ripened wall of the ovary, and by considering its strong or weak construction, its dry or pulpy condition, as a secondary matter. It is obvious that the whole theory of the flower was thus placed upon a better basis, since dry indehiscent fruits may come from inferior or superior ovaries. But Gärtner’s theory of the seed is one of his most valuable contributions to the science. After careful consideration of the seed-envelopes, he submitted the inner portion (nucleus) enclosed by them to a searching comparative examination; he correctly distinguished the endosperm from the cotyledons, and described the variations in its form and position. This was the more needful, since Linnaeus had denied the existence of an ‘albumen’ in plants, which Grew had already recognised and so named; to Linnaeus it appeared to be of no use to the seed. Though Gärtner speaks of the cotyledons as uniting with the embryo to form the nucleus of the seed, yet his account shows that he regarded them as outgrowths of the embryo itself. The uncertainty which still existed in the interpretation of the parts of the seed is shown even in Gärtner by his curious notion of a ‘vitellus,’ which in fact takes in everything that he was unable to explain aright inside the seed; for instance, he makes the scutellum in grasses, and even the cotyledonary bodies of Zamia a vitellus, and applies the same name to the whole contents of the spores of Seaweeds, Mosses, and Ferns. In spite of the striking defects connected with this mistaken notion in his theory of the seed, his views far surpass in clearness and consistency all that had hitherto been taught on the subject. His giving the term embryo to that part of the seed which is capable of development was also an advance in respect of logic and morphology, in spite of his mistake in not admitting the cotyledons which are attached to the embryo into the conception; this, however, could easily be corrected at a later time. What Gärtner now named the embryo, had been up to his time called the ‘corculum seminis,’ especially by Linnaeus and Jussieu; it was evidently thought that Cesalpino’s phraseology was thus retained; but he, as we have seen, understood by the words ‘cor seminis’ the spot where the cotyledons spring from the germ, which spot he wrongly took for the meeting-point of root and stem and the seat of the soul of the plant. And so at last after two hundred years the word disappeared from use, which might have reminded the botanist of Cesalpino’s views respecting the soul of plants.

A work such as Gärtner’s could scarcely find a fruitful soil in Germany, where some thirty years before even Koelreuter’s brilliant investigations had met with little sympathy, and Conrad Sprengel’s remarkable enquiries into the relations of the structure of the flower to the insect-world in 1793 failed to be understood; Gärtner complains in the second part, published in 1791, that not two hundred copies of the first volume were sold in three years. But the work, which forms an epoch in the history of botany, was better received in France, where the Academy placed it as second in the list of the productions which in later times had been most profitable to science; there lived the man who was able to measure the whole value of such a work—Antoine Laurent de Jussieu. But even in Germany, where plant-describing was comfortably flourishing, there were not altogether wanting men who knew how to estimate both the services of Gärtner and the importance of the natural system. First among these was August Johann Georg Karl Batsch, Professor in Jena from 1761 to 1802, who published in the latter year a ‘Tabula affinitatum regni vegetabilis,’ with characters of the groups and families. Kurt Sprengel, who was born in 1766, and died as Professor of Botany in Halle in 1833, contributed still more to the spread of clearer views respecting the real character of the natural system and the task of scientific botany generally by numerous works, and especially by his ‘Geschichte der Botanik,’ which appeared in 1817 and 1818. But even this highly gifted and accomplished man agreed with the Linnaean botanists in attributing an excessive value to the describing of plants, as is shown in his history, where to exalt the merits of the old botanists he gives figures of the plants first described by them.

Meanwhile the meritorious efforts of these men were not in themselves capable of directly advancing the natural system, or of greatly increasing the number of its adherents in Germany, nor did it find general acceptance in that country till it had made considerable progress in the hands of the two foremost botanists of the time, De Candolle and Robert Brown.