Imatges de pàgina

public at large, and I may venture to say that the result has surpassed my expectations. But the progress which the higher and scientific knowledge of plants has lately made, seemed to demand an introductory treatise for the use of students, which, embracing the discoveries that have recently been made throughout the whole extent of the science, might supply the place of the introductory work of Willdenow now become completely useless. With the help of the latest edition of Decandolle's Theorie Elementaire de la Botanique," published at Paris, 1819, I flatter myself that I have been able to present to the public such a work. But only the first three parts of this treatise, namely, the Nomenclature, the Theory of Classification, and Descriptive Botany, are to be considered as extracts from the book of my excellent friend. All the rest is my own; and the reader will perceive that I have used. my utmost exertions to fulfil well the task I had undertaken." Sprengel's Preface.

The names of the authors of this work are by no means new to the scientific world: the Flore Françoise, and other works of Decandolle, have acquired him high and deserved reputation. Sprengel is best known in this country, as the author of an excellent treatise on Cryptogamous plants. The general arrangement of the work is similar to that of the Principles of Botany," of Willdenow; in the first department of the work styled "Nomenclature" (the term Terminology being objected to) there are some valuable rules for the formation of botanical language. In several parts, however, there is much useless multiplication of terms: as for instance in the article Nectary; the term Nectary is confined to the organs which secrete honey, while the other parts that have usually received this name are divided into Nectaro-thecæ, Nectari-lymata, and Nectaro-stigmata. Linnæus certainly may have gone too far in designating every unusual appearance in a flower, a Nectary; yet the term has been found extremely convenient, and is now generally adopted in the extended signification; and as there is no fear of confounding it with any of the more essential parts of the flower, the propriety of the change of name is very questionable: considering that the author continues to call the subdivisions of the footstalks of leaves nerves and veins, there is little occasion, in this particular instance, for fastidiousness about physiological correctness in nomenclature.

Part 2nd, Taxonomy, contains a view of the principal systems of classification, beginning with the artificial system of Linnæus, the several advantages and defects of which are very fairly stated; then follows an account of the mutual

connection of plants as regards class, order, genus, and species. The following is a very apt illustration of the distinction between species and variety.

"When for instance in the common Lotus corniculatus, on whatever soil it may grow, we uniformly observe that it has a solid stem, even and erect divisions of the calyx, and expanded filaments, we must of necessity distinguish as a particular species from it, another form which grows in bogs and watery meadows, which has a much higher and always hollow stalk; the divisions of its calyx spread out into a star-shape, and hairy, and which has uniformly thin filaments, and we must name this latter species either Lotus uliginosus with Schkuhr, or Lotus major, with Scopoli and Smith. As on the other hand, the Pimpinella Saxifraga grows sometimes quite smooth, and sometimes in woods and shady meadows considerably hairy, as it displays sometimes simple and small stem leaves, sometimes half and even doubly pinnated leaves; and as these forms vary according to the situation of the plant, and during re-production, we cannot regard these forms by any means as distinct species, but we must view them as corruptions."

In speaking of the links of connection of the vegetable kingdom, with a view to the natural arrangement of plants, the author attempts to trace most of the varieties in the figure and structure of their several organs, to a few simple original forms, which are considered as the standards, all the deviations from which are the effect of abortion, or the result of the union of parts originally separated. From some examples which are cited, this theory appears at first somewhat plausible, but in the instance of the class Tetradynamia, it is carried beyond all reasonable bounds. The plants of this class, the author supposes to have originally belonged to Decandria, and that the four petals of the former are merely altered filaments, " as in Thlaspi Bursa we sometimes observe this return to the original structure. Surely it would be more philosophical to conclude, that Thlaspi Bursa occasionally deviates from its accustomed structure, than to accuse nature of such an extensive system of abortions. When we consider the numerous and striking characters which distinguish the plants of this class, and which seem almost to mark them as a separate and insulated province of the vegetable kingdom, the idea of their being mere alterations of other more primitive and established forms, must at once be rejected.

As far as regards the 4th Part of the work, "Phytotomy,”

we cannot altogether agree with the translator in the high encomiums he has pronounced on the work in his preface.

"That in no one part is it possible to discover a trace of that visionary mode of considering facts, and appearances which has been unjustly represented as belonging to all German writers; that condensation and perspicuity are among its most striking excellencies;-that it bears in all respects evidence of having proceeded from men, who not only knew their subject extensively and well, and who thought justly on all its parts, but of men, who were in possession of the best means of conveying their information with effect, or who had made the higher laws of composition their study."

In this department, at least, which Sprengel tells us is "all his own," the style and mode of reasoning are far from possessing the pre-eminent qualities imputed to them by the translator. We do not recognize here the simplicity and elegance of Mirbel, who, although he has given a most minute and detailed account of the varieties in the structure. of vegetables, has, by his decided and well arranged description, rendered the anatomy of plants at once intelligible, beautiful, and satisfactory.

Sprengel divides the vegetable textures into three primitive forms, the cell-form, the tube-form, and the spiral form; the origin of the cells and tubes is thus explained.

"Every organizing fluid, when it is passing from the fluid into the solid state, shews small spheres or vesicles, and speculæ, or needle-shaped bodies of a diminutive size. The former we refer to the disengagement of hydrogen, which, as one of the constituents of water, is always the first to separate itself from it, because it is little soluble in water. Oxygen, on the other hand, remains longer dissolved in water, and accordingly the spicular and straight lined bodies which are produced by it are more slowly disengaged, as in an electrical process, negative electricity displays sparks and images of a spherical shape, whilst positive electricity produces those of a spicular appearance. We find this same combination of spherulæ and spiculæ in every generative sap, as well as in every slimy fluid of plants. From these, therefore, are solved the peculiar primitive forms of the veget able world."

The cellular texture is termed the perfection of the spherical formation, and the tubular that of the spicular.

Now if cells and tubes were original chemical formations, and were produced by two substances of totally opposite properties, it is obvious that they must always remain perfectly distinct from each other, and could never be found in an

intermediate state. In the following observations therefore the author completely overturns his gazeous hypothesis.

"The stretched form of the cells is very like the tube-form. It is even undeniable that it constitutes, especially in the lower organic bodies, the transition form from the cells to the tubes. In the fruit stalk of the Musci Hepatici and Frondosi, we have not yet discovered the proper tube form, but only stretched cells similar to tubes, which apparently answer the purpose of these latter bodies."

The author (§ 273) advances the doctrine of organic perspiration through impervious texture; this is very difficult to comprehend; it is much more probable that the small size of the pores in the cellular tissue, the epidermis, and other parts, has occasioned them to escape observation. The following is the opinion of Mirbel on this subjeet. (Elemens de Physiologie Végétale et de Botanique. Paris. 1815.)

"Un tissu membraneux, cellulaire et continu, plus ou moins transparent, forme toute la substance des vegetaux. La membrane qui constitue le tissu membraneux est d'une épaisseur variable selon la nature particuliere des especes et l'âge des individus. Elle est pourvue de pores, les uns visibles, les autres invisibles. L'existence de ces derniers est prouvée par la transfusion des fluides d'une partie du végétale dans une autre, lors même qu'il est impossible d'appercevoir la communication de cellules; l'existence des autres est prouvée non-seulement par la marche des fluides, mais encore par l'observation microscopique, qui fait distinguer nettement les pores et les fentes dont souvent la membrane est criblée."

Since Mirbel is now generally considered the best authority, in Vegetable Physiology, and as Sprengel has most unaccountably neglected him, it may not be irrelevant to mention, that these two eminent philosophers are old antagonists. Mirbel published his " Traité d'Anatomie et de Physiologie Végétale in the year 1802: according to Sprengel, this contained many errors, and " in the mean time," he states, "Link, Rudolphi, and Treviranus, published more correct views; since then Mirbel has come nearer the truth. (Exposition et Défense de ma Theorie de l'Organisation Végétale. Amsterdam. 1808.)"

But Mirbel, on the contrary asserts, that his works, from an imperfect knowledge of the language, or some other cause, were misunderstood, and misrepresented by several German authors, especially by Sprengel; and that the pamphlet which he published at Amsterdam, merely contained more complete view of his former opinions. For a full statement of

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the discussions on this subject, the reader is referred to Mirbel's "Exposition et Defense de la Theorie de l'Organisation Végétale. Paris. 1809.

The spiral form of vessels, the author divides into the primitive, and the derived; the latter which he calls Vasa scalaria, are the false spiral tubes (fausses trachées) of Mirbel:

<< Under this name are included those canals with transverse openings, which do not at all shew the spiral winding of the fibres, and which cannot be unrolled. They are formed by an original spiral vessel meeting with perpendicular fibres in its sides, which fibres cross the winding lines longitudinally, and unite them together."

Notwithstanding Sprengel has seen the perpendicular fibres, after maceration, we cannot help suspending our assent to his opinion of the structure of these vessels: since from their position, and from the circumstance of their not being accompanied by the true spiral vessels, it seems most probable, that they are original vessels, resembling the more simple sap vessels, and differing from them merely in the size of their openings. With respect to the uses of the spiral tubes, the author adopts the old opinion, that they are air vessels, and perform some more important office than the common sap vessels.

"As then the spiral vessels, and all their varieties are uniformly found empty of fluids, as they shew themselves only in the higher plants, and constantly appear wherever a strong shoot is sent out; as they are always in the company of the sap vessels; as in fine they maintain by their constant diagonal direction, the middle situation between the perpendicular and the horizontal: from all these considerations we must suspect, that they are the instruments of the higher, vital activity of plants, and that they are the organs by which the sap tubes suffer an external excitement to the speedy propulsion of the sap."

The following is an ingenious explanation of the cause of the green colour of leaves.

"The exhalation of oxygen gas is closely connected with a remarkable property of leaves, namely, their green colour. As this colour in the rainbow stands exactly in the middle, between the two outermost tints, the red and the violet,-as it is bounded on the one side by the yellow, and on the other by the blue,-as all experiments further shew, that the red and yellow tints are more of an oxygenous, and the blue and violet more of an hydrogenous nature, it is extremely probable, that the green colour is the effect of a neutralization between the two extreme colours, or that

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