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new species discovered have been arranged according to its principles of classification, and most catalogues of plants, and floras,* have taken this method for their guide.
The characters used in this system are very apparent; and as it refers to the number of parts, rather than to their forms or insertion, it offers to the mind something positive, which is not found either in the method of Tournefort, or that of Jussieu. Between a corolla, bell form or funnel form, there are many intermediate forms, which may be as much like one, as the other. The insertions over the germ, or under the germ, are distinct, but between them, is the insertion around the germ, which sometimes blends with one, sometimes with the other. But between one or two stamens, or one or two pistils, there is no intermediate step, or gradual blending of distinctions, which leaves you in doubt whether the case before you belongs to the one, or the other.
The natural orders of Linnæus are 58; they are not founded upon any one principle, but upon general marks of resemblance. This great man did not view his Natural Orders as approaching to a perfect classification; he modestly termed them “Fragments of a natural method.” As every thing left by him on the subject of botany seems deserving of consideration, his Natural Orders are preserved as a relic, which it would be almost sacrilege to destroy : there is in them more of simplicity than in those of Jussieu, and they may be better understood by the young student.
Linnæus, in his « Philosophy of Botany," has established three kinds of characters to be used in descriptions of plants.
1st. Factitious (or made). That which is, by agreement, taken as a mark of distinction : thus the number of stamens and pistils is fixed upon for distinguishing some of the classes and orders. Although nature has formed these organs, the arrangement of plants by their means, is an invention of man, or artificial.
2d. Essential Character. That which forms a particular character of one genus, and distinguishes it from all other genera.
3d. Natural Character. This is difficult to define, though it is that which is understood by all ; it is the general aspect and appearance of the plant which enables all persons to
* The term flora is often used for the title of a book describing plants. The ancient heathens imagined a goddess called Flora, who, they thought, presided over flowers.
System of Linnæus offers something positive---Natural orders of LinnæusThree kinds of characters to be used in descriptions of plants-Factitious character-Essential character-Natural.
make a kind of arrangement of plants in their own minds, although they would find it very difficult to convey their ideas of classification to others.
It is by their natural characters, that persons who have never, perhaps, heard of such a science as zoology or the classification of animals, are enabled to distinguish ferocious beasts from domestic and gentle animals; they see a sheep or cow without any terror, although that individual one they may never have seen before ; for nature teaches them to consider that, as resembling other sheep and cows, which they know to be inoffensive.
This natural character teaches savages to distinguish among the many plants of the forest, those which may administer to their wants and those which would be injurious.
Even the lower grades of animals have this faculty of se. lecting by natural characters, nutritious substances, and avoid. ing noxious ones ; thus we see the apparently unconscious brutes luxuriating in the rich pastures prepared for them by a benevolent Creator, and cautiously passing by the poisonous weed, directed by the curious instinct given them by this same Almighty Benefactor.
Characters used in classification. A natural family is composed of several genera of plants which have some common marks of resemblance, and its name is usually founded upon this general character; as Labiate and Cruciform, which are derived from the form of the corollas; Umbellate and Corymbiferous, from the inflorescence; Leguminous from the nature of the fruit.
Families resemble artificial orders in being composed of genera, but the principles on which the genera are brought together, differ widely in the two cases.
In natural families, the classification is such as persons who have never studied botany, might make ; thus, dill, fennel, caraway, &c. belong to the Umbellate family, on account of the form in which the little stalks, bearing the flower, and afterwards the seed, branch out from one common centre, like the sticks of an umbrella ; this general resemblance is observ. ed by all, and it seems very natyral to class such plants together.
Animals capable of discerning these natural characters Families of plants -In what respect do families resemble artificial orders? How do they differ? -Persons might form natural families without a knowledge of botany.
But in the artificial orders, genera
very un. like in other respects, are brought together, from the single circumstance of their having the same number of stamens and pistils. Thus, in the first order of the 8th class we have the tulip and the bulrush, the lily of the valley and the sweet flag. In the second order of the 5th class we have the beet and the elm. You will at once perceive the striking disparity between these plants, and that an arrangement, which thus brings them together, is properly called an artificial method.
Many families of plants possess a marked resemblance in form and qualities, and appear evidently as distinct tribes. If the whole of the vegetable kingdom could thus be distributed into natural classes, the study of botany would be much simplified; but it has already been remarked that there are many plants which cannot be thus arranged, and no principle has yet been discovered for systematic arrangement which bears any comparison to the Artificial System. This system is compar. ed to a dictionary ; though by its use we do not at first find the word for which we seek, and then learn its definition, as we do in dictionaries of terms; but we first learn some of the characters of a plant, and by these as our guide, we proceed to find the name. We are not however to rest after finding the botanical name ; but having ascertained this, we can easily find to what natural family a plant belongs, and thus ascertain its habits, medicinal use, and other important particulars. The natural method may then be considered as the grammar of botany ; between this and the artificial system, the same relation exists, as between the grammar and dictionary of a language ; both are necessary to science.
As the subject of classification is so important to a knowledge of botanical science, we will now consider the general princi. ples on which it depends.
Rules. 1st. All botanical classification results from an examination and comparison of plants.
2d. Every organic distinction which establishes between indi. viduals any resemblance, or any difference, is a character; that is, a sign, by which they may be known and distinguished.
3d. The presence of an organ, ils different modification and its absence, are so many characters.
4th. The presence of an organ furnishes positive characters, its absence negative characters.
Genera in the artificial orders brought together by having the same number of stamens and pistils –Artificial system of arrangement compared to a dietionary - First learn the characters, then the name-The natural method considered as the grammar of botany—Mention the first four rules which are given for classification.
Positive characters offering means of comparison, shew the resemblances and differences which exist between individuals ; those plants in which these characters present but slight differences, should be collected in groups; those in which these characters differ more sensibly, should be separated; here we follow strictly the laws of the mind. But negative characters, as they allow no comparison, can only be employed to separate individuals, and never to bring them together.
When we say that plants have seeds with one or two cotyledons; that they have monopetalous or polypetalous flowers, and are provided with stamens and pistils, we point out particu. lars, where visible and striking resemblances may be observ. ed; these characters, then, are positive, since they are founded on something real.
When we say that some plants are destitute of cotyledon, corolla, stamens or pistils, we do not establish any real basis for the foundation of a comparison. If we wish to separate plants with monopetalous corollas, from such as have polypeta. lous corollas, this single character establishes at once, the difference which exists between the two groups, and the resem. blance, which exists between the individuals of each group. Thus positive characters possess a great advantage over negative ones; the latter should never be employed when the former can be used; and in proportion, as positive characters can be substituted for negative, the science of botany will be perfected.
Positive characters can only be founded upon evident facts, and never upon a presumption of the existence of facts, derived from analogy. For it is contrary to true philosophy, to suffer hypothetical reasoning to usurp the place of direct observation of facts,
5th. Positive characters are constant or inconstant. All seeds produced by plants of the same species have the same structure; all plants which grow from these seeds, produce other seeds, similar to those from which they have had their origin : of course the characters derived from the structure, of these seeds are constant. But
among these plants some are large and others small ; some may have white corollas, some, red, or blue; some are more fragrant than others; of course, size, colour and odour offer inconstant characters.
6th. All real science in botany must rest upon constant characters; therefore, these characters are much more important than the others.
Positive and negative characters-Give illustrations of these characters, with their uses-Advantage of positive characters over negative-Founded only upon evident facts - What is the fifth rule?--The sixth ?
7th. Constant characters may be isolated or coexistent. The petals of the RANUNCULUS acris (butter-cup) have a nectary in the form of a scale; this character, although constant, is isolated, for it is not necessarily connected with any other char. acteristic trait. The calyx of the campanula rotundifolia, (blue-bell,) adheres to the germ; the germ must of necessity be simple, or without divisions, and the corolla and stamens attached to the interior of the calyx. The character of the adherence of the calyx to the germ, brings in its train several other characteristics ; it is then coexistent; and is more impor. tant than the isolated character.
8th. Two orders of characters are derived from the two great divisions of vegetable organs ; those of vegetation and reproduction. The charaiters of vegetalion are few, and mostly isolated ; the characters of reproduction are numerous and often coexistent ; one character serving as an index to many others.
It is seldom that plants which resemble each other in their characters of reproduction, differ much in their characters of vegetation. For example, all plants which have four didynamous* stamens, attached to a monopetalous labiate corolla, and four seeds lying uncovered in a monophyllous calyx, have an angular stem and opposite leaves. On the contrary it frequently happens, that plants which resemble each other by the characters of vegetation, differ by those of fructification. Labiate and caryophyllous plants agree in having their leaves opposite, and yet there is no resemblance in their flowers. This consideration alone, would seem sufficient for establishing the superior importance of the characters of reproduction over those of vegetation. The seed unites in itself the char. acters both of reproduction and vegetation. The embryo is the commencement of the new plant, and it offers us the first characters of vegetation; but its situation in the fruit, the number, form and consistence of its envelope, are characters which belong to fructification.
As far as possible, in separating or bringing together plants, we should make use of prominent characters which the eye can see, without the help of the microscope ; but if experience teaches us that the characters most constant and proper for the explanation of physiological phenomena can only be discover. ed by such aid, it is necessary to resort to this instrument, in order to establish the natural relations of plants.t
* That is, two long and two short stamens.
† The foregoing rules and observations respecting characters for classification, are translated from Mirbel's “Elemens de Botanique.”
The seventh ?-The eighth ?-Characters of reproduction more important than those of vegetation-In what cases should we make use of characters invisible to the naked eye?