The three distinct treatises of which the Praeludia Botanica consists were written probably at different times, though published simultaneously in 1669. The first of them is an alphabetical catalogue, comprising about 2600 species, of the plants in the Royal garden at Blois when under Morison's care: 260 of the species are marked as new, and are fully described in an appendix. But the chief interest of the Hortus Regius Blesensis Auctus lies in the dedication to King Charles II. Morison here narrates how, whilst at Blois, he had framed a system of classification; how the King's Uncle, the Duke of Orleans, had promised to undertake the publication of a book to illustrate the system on an adequate scale, and how the sudden death of the Duke in 1660 had destroyed all such hopes; and he ends by appealing to the King to give him the patronage that he so much needed. "Quod si annuere hoc mihi digneris," he wrote, "polliceor Britanniam vestram cum methodo exactissima (quae est naturae ipsius) imposterum, in re Botanica gloriari posse, quemadmodum Italia, Gallia, Germania, superiori saeculo, sine methodo, in Scientia Botanica gloriatae sunt." But the King does not appear to have been moved by this dazzling promise. Morison evidently did not suffer from any lack of confidence in himself or in his method, of which he speaks on a previous page of the dedication, as "methodus nova a natura data, a me solummodo (citra jactantiam) observata: a nullo nisi meipso in hunc usque diem detecta, quamvis mundi incunabilis sit coeva," language which can hardly be described as modest. And yet, curiously enough, Morison gives not the slightest indication of the principles of this altogether new and original method of classification.
The second treatise, the Hallucinationes, is a searching and acute criticism of the published works of the brothers Bauhin: of the Pinax of Caspar, and of the Historia of John. Though he acknowledges in the preface the great value of their botanical labours, Morison did not fail to set out in detail the mistakes that they had made in both classification and nomenclature, and to make corrections which were, for the most part, justified. Probably it was the critical study of the works of the Bauhins that led Morison to frame a system of classification of his own.
The third and last treatise is the Dialogus: a dialogue between himself, as Botanographus Regius, King's Botanist, and a Fellow of the Royal Society, on the theme of classification. Here again Morison asserts the superiority of his own method: "Methodum me observasse fateor: estque omnium quae unquam adhuc fuerunt exhibitae, praestantissima et certissima quippe a natura data." But he still fails to give any definite account of it: all that he says amounts merely to this, that the "nota generica" is not to be sought in the properties of a plant, nor in the shape of its leaves, as had been suggested by earlier writers, but in the fructification, that is, in the flower and fruit (essentiam plantarum desumendam ... a florum forma at seminum conformatione).
The mention of a system of classification based on the form of the leaf evoked from Botanographus a pointed allusion to a book recently published by a Fellow of the Royal Society in which such a classification had been used, with the following severe comment: "Ego tantum confusum Chaos: illic, de plantis legi, nec quicquam didici, ut monstrabo tibi et lapsus et confusionem, alias." The book so criticised was the encyclopaedic work edited by Dr John Wilkins, Bishop of Chester, and published by the Royal Society in 1668, entitled, "An Essay towards a Real Character and a Philosophical Language," to which John Ray had contributed the botanical article 'Tables of Plants.' This criticism was the beginning of the unfriendly relations between Morison and Ray, of which some further account will be given subsequently.
Another point of interest in the Dialogus is the definite assertion (p. 488) that Ferns are 'perfect' plants, having flower and seed (quia habent flores, qui fugiunt quasi obtutum, et semina quasi pulvisculum in dorso alarum), an assertion which was repeated with even greater emphasis in Morison's preface to his edition of Boccone's Icones at Descriptiones Rariorum Plantarum etc. (Oxon. 1674), in opposition to the views of earlier writers, Cesalpino in particular. Cesalpino had, it is true, said of the group in which he had placed the Ferns and other Cryptogams, "quod nullum semen molitur" (De Plantis, p. 591): but he had added, in the same paragraph,—"ferunt enim in folio quid, quod vicem seminis gerit, ut Filix et quae illi affinia sunt." It is a question if Morison was much nearer the truth than Cesalpino.
It is in the preface of his Plantarum Umbelliferarum Distributio Nova (1672) that Morison first gave a definite statement of the principles of his method, in the following terms: "Cumque methodus sit omnis doctrinae anima: idcirco nos tam in hac umbelliferarum dispositione, quam in universali omnium stirpium digestione, quam pollicemur, notas genericas et essentiales a seminibus eorumque similitudine petitas, per tabulas cognationis et affinitatis disponentes stirpes exhibebimus. Differentias autem specificas a partibus ignobilioribus, scilicet radice, foliis et caulibus, odore, sapore, colore desumptas adscribemus, singulis generibus singulas accersendo species: ita species diversa facie cognoscibiles, sub generibus intermediis: genera intermedia sub supremis, notis suis essentialibus et semper eodem modo sese habentibus distincta militabunt. Hic est ordo a natura ipsa stirpibus ab initio datus, a me primo jam observatus."
It is not necessary to discuss in detail the merits of Morison's work on the Umbelliferae. It will suffice to say that it was published as a specimen of the great Historia that he had in preparation—trigesimam operis quod intendimus partem—so that the learned world might have some idea of what they were to expect from the completed work "quemadmodum aiunt ex ungue leonem"; and further, that it was the first monograph of a definite group of plants, and is remarkable for the sense of relationship between the genera that inspires it. The Umbelliferae constituted Sectio IX among the fifteen sections in which Morison distributed herbaceous plants.
At length, in 1680, appeared the Pars Secunda of the Plantarum Historia Universalis Oxoniensis in which work Morison's long-expected method of classification was to be exhibited and justified. However in this respect it proved to be disappointing: partly because it was so limited in its scope, dealing with but five of his fifteen Sectiones of herbaceous plants: and partly because it did not contain any complete outline of his system. It is most singular that, although he wrote so much, Morison should have died without having published any more definite information concerning his system of classification than what has been here cited.
Morison's influence did not, however, cease with his death; his tradition was maintained by the publication in 1699 of the Pars Tertia of the Historia, under the editorship of Bobart. This volume threw some welcome light upon Morison's system, inasmuch as it completed the description of the herbaceous plants, and gave a clear statement, in the form of a Botanologiae Summarium, of the classification resulting from the application of Morison's principles to these plants. But, even so, the revelation of the system still remained incomplete, in the absence of any account of the trees and shrubs.
It was not till nearly forty years after Morison's death, not until Bobart too was dead, that a full statement of Morison's method was published. In 1720 there appeared at Oxford a small tract of but twelve pages, the Historiae Naturalis Sciagraphia, containing an account of a complete system of classification, which agrees in all essentials, so far as herbaceous plants are concerned with that adopted by Morison and by Bobart in their respective volumes of the Historia: and, as regards trees and shrubs, with that in the MS. volume by Bobart which has been already mentioned. The tract is anonymous, but the matter that it contains is Bobart's work, whether it was written by himself or by some one who had access to his papers. This classification may be accepted as being essentially that of Morison, though somewhat modified by Bobart, who had undoubtedly been influenced by Ray's systematic writings which had appeared meanwhile. It is of such interest that it may be reproduced here, somewhat compressed, with an indication of the modern equivalents of the groups.