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Different species, even in the same genus, sometimes differ in their stems ;, some being woody and others herbaceous. Neither is the form of the corolla to be depended on; even in the most natural families of plants, we find flowers of different forms, as in different species in the natural order Solaneæ, where the mullein is wheel-form, the tobacco funnel-form, and the atropa bell-form.
System of Linnæus. We shall not now attempt to give a view of the system of Linnæus, as we are hereafter to consider it in detail. We introduce it here merely to compare it with other modes of classification. The removing of plants which are nearly allied in their natural character, to different classes, by means of any artificial principle of classification, ought as far as possible to be avoided ; and although the system of Linnæus, as you will find, when we compare it with natural families, is not wholly free from this confusion, it is much more so than any other which has been invented.
Although we do not now receive the method of Tournefort, for practical uses, a knowledge of it may extend your views of botanical science. When we accustom ourselves to take but one view of a subject, we are in danger of acquiring a contract. ed mode of thought. We are not to suppose that the system of Linnæus is entirely perfect; but may well imagine that men of science will arise, who shall discover principles now hidden, and look back upon what they will call, the very imperfect state of our sciences. We should rejoice that the human race is thus destined to a degree of improvement beyond our highest powers of calculation.
“ What should we think of a savage, if, in the pride of his ignorance, he was to conceive his own thoughts and feelings to be the noblest of which the human intellect is capable? And perhaps even the mind of a Newton, is but the mind of such a savage compared to what man is hereafter to become."*
The system,t of Linnæus has already in its principal features been laid before you, in the views of artificial classes and or
† System differs from method in having but one single primitive character, and in founding its principal divisions upon the consideration of only one single organ or principle. Linnæus founded his system upon the consideration of the stamens as more or less numerous, upon their proportion, connexion, and their absence. Newton founded his system of Natural Philosophy upon attraction. The vital principle is the foundation of all systems of Physiology: Method is not confined to the consideration of one character; it employs all such as are conspicuous and invariable.
System of Linnæus not entirely perfect--Advantages of taking different views of a subject - Human mind destined to progressive improvement-Difference between system and method (see note).
system not only includes within it all known plants, but is founded on such principles as must comprehend within it whatever plants may yet be discovered. Its author believed that no plant was destitute of stamens and pistils : but at the same time, that there were species in which these or. gans were so small, so obscure, or of such a singular formation as to render it difficult, and sometimes impossible to be certain of their existence, except by the principle of analogy. There. fore, he made the two grand divisions of plants, Phenogamous, such as have stamens and pistils visible, and Cryptogamous, stamens and pistils invisible.T
The following comparison has been very properly made by Botanists, as an illustration of the divisions in the system of Linnæus.
Classes are compared to States.
to Families. Species,
to Individuals. You must not forget, while considering this system, that plants themselves are the only real substances ; species, genus, order and class, are mere abstract terms, denoting certain distinctions which would equally have existed, although we had never observed them, or given them names.
An Individual is an organized being, complete in its parts, distinct and separate from all other beings.
An oak, a rose, and a moss, are each of them individuals of the vegetable kingdom.
A Species includes such individuals as agree in certain circum. stances of the roots, stems, leaves and inflorescence. We have no reason to suppose that any new species, either of animals or vegetables, have been produced since the creation. times see varieties in plants made by cultivation; the stamens and pistils, from excess of nourishment, expanding into petals. Varieties are also occasioned by strewing the pollen from one species, upon the stigma of another; but these varieties do not produce perfect seed, and therefore cannot reproduce them. selves by their seed. The colour, taste and size, are not considered as marks of specific difference.
A Genus comprehends one or more species, grouped togeth. er on' account of some resemblance in situation, proportion, and connexion of the organs which constitute the flower. Any
* See part I, page 29.
+ Mirbel believes there are some plants absolutely destitute of stamens and pistils; these he calls agamous.
System of Linnæus provides for the classification of such plants as are yet to be discovered - Illustrations of its divisions-Plants the only real substances - Individual-Species - Genus.
one species of a genus may be regarded as a type or example of the others; we may easily refer species which we have not studied to their proper genus, by a knowledge of any one spe. cies of that genus. Some genera appear to be distinctly marked by nature; the various species of the rose, form a beautiful genus which is known to all, although every one might not be able to describe it to others, in such a manner as to be understood; it is chiefly distinguished by its urn-shaped and fringed calyx.
The Generic names of plants are derived from various cir. cumstances ; in some cases from a peculiarity of form or colour of the corolla or some property of the plant, and some are named from distinguished persons.
Thus Iris, (flag,) is named from Iris the rain bow, on account of its various shades of colour.
Digitalis, (fox-glove,) named from digitus, a finger, on account of the shape of its corolla, like the finger of a glove. Convallaria, (lily of the valley,) named from a Latin word convallis, signifying valley.
Teucrium (germander,) named in honour of Teucer, a Trojan prince, who is said to have discovered this plant. The Eng. lish name, germander, is supposed to have originated from the word Scamander, the name of a river of ancient Troy.
The name of the great Linnæus is commemorated in a beautiful and modest flower, called the Linnæa borealis.* Specific names are generally adjectives; generic names are
The specific name sometimes indicates the number of leaves, as orchỊs bifolia, (bifolia, signifies two leaves,) or the colour of the corolla ; as vioLA, tri-colour, (three coloured violet,) or the form of the root; SOLANUM tuberosum ; (with a tuberous root ;) specific names are also derived from the names of persons; thus a species of Origanum is named tourneforti, after its discoverer Tournefort.
Method of Jussieu. The natural method consists in bringing together such plants as seem by nature to be constituted one family, resembling each other in general appearances and medicinal qualities; as lilies, herbs, trees, mosses and ferns. Some of these natural
Borealis signifying northern, has reference to the situation of the country which gave birth to Linnæus. The Linnæa borealis is not uncommon in New England, and has been found on an Island, in the Hudson, near Troy.
A knowledge of one species in a genus enables us to recognize all other species of the same genus-Derivations of generic names Generic names Iris-Digitalis - Teucrium-Linnæa borealis-Specific names-Natural method.
families show a similarity in form and quality, and are evident-
The characters employed in this method are,
1. The Seed, considered with respect to Cotyledons.* A plant without cotyledons is called, A'cotyledonous, with one, Mono'cotyledonous, and with two, Di'cotyledonous.
2. The Stamens are inserted above the germ, under the germ, or around the germ: the 1st is Epi'gynous, the 2d Hypo'gynous, the 3d Peri'gynous.
3. A'petalous, having no corolla, Mono' petalous, all of one piece, or Poly'petalous, many petals.
4. Mono'clinious, Stamens and Pistils on the same corolla, Di'clinious, Stamens and Pistils on different corollas. 5. Anthers distinct, or anthers joined.
Synopsis of Jussieu's method. ACOTYLEDONS,
CLASS 1 Stamens hypogynous,
* The Cotyledons are the thick parts of the seed ; an apple seed, an orange seed, or a bean, may be easily split into two parts; these are the cotyledons ; nice and wheat cannot be thus split, they have but one cotyledon.
Many plants cannot be referred to any natural families--Two natural methods to be considered--What are the characters employed in Jussieu's method ? -How is the structure of the seed considered --How the insertion of the stamens !-How the corolla ?--How the anthers ?–Give a synopsis of Jussieu's method.
5 apetalous. perigynous,
7 Corolla hypogynous,
10 combined, epigynous, anthers
distinct, Stamens epigynous,
12 polypetalous. hypogynous,
15 These classes are divided into 100 orders';* but they are obscure and indefinite in many particulars. The dicotyledons include the Cryptogamous plants of Lin.
The monocotyledons consist of three classes; grasses, palms, and liliaceous plants. The dicotyledonst form the 11 remaining classes.
There are some genera which appear so ambiguous in their character, as to render it doubtful where they should be placed.
In the three methods of classification which we have now examined, the most important characters of the plant have been presented, under circumstances calculated to give you more clear-ideas of them, than could have been obtained from a con. sideration of any one method, alone.
Tournefort makes you acquainted with the different appear. ances of the corolla.
Linnæus, of the stamens and pistils.
The method of Tournefort cannot be relied on, because the forms of corollas vary into each other; that of Jussieu, considered as a study in itself, is much too abstract; the number of cotyledons, generally speaking, is an excellent character, but you cannot in the beginning appreciate its value; and as to in. sertion, botanists themselves are sometimes embarrassed to decide respecting it. This method, although much admired, has been little used; on the contrary, the method of hæus has been for half a century the foundation of all teaching. The
* See Part I, page 39.
+ The dicotyledonous division includes also the Polycotyledons, or a few plants with more than two cotyledons.
How many of Jussieu's orders ?- Acotyledons-Monocotyledons-Dicotyle dons—The three methods of classification considered, present the most important characters of the plants under different points of view--Comparison of these methods.