lies, 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 ake but one view of a subject, we are in danger of acquiring a contracted mode of thought. We are not to suppose that the system of Linnæus is 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," says an elegant writer,* "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 of Linnæus has, in its principal features, been laid before you. This 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 organs were so small, so obscure, 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. Therefore, he made the two grand divisions of plants, Phenogamous, such as have stamens and pistils visible, and Cryptogamous, stamens and pistils invisible.§

You must not forget, that 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. We sometimes 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 such plants do not produce perfect seed, and therefore cannot reproduce themselves. Colour, taste, and size, are not considered as marks of specific difference.

*Dr. Thomas Brown.

+ 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.

See Part I, page 24.

§ Mirbel believes there are some plants absolutely destitute of stamens and pistils these he calls agamous.

Advantages of taking different views of a subject-Human mind destined to pro. gressive improvement-What is the difference between system and method? See note -What is said of the system of Linnæus-The terms species, genus, &c.—What is an individual -- What is a species ?

A Genus comprehends one or more species, grouped together on account of some resemblance in situation, proportion, and connexion of the organs which constitute the flower. Any 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 species 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 circumstances; in some cases from a peculiarity in the 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 rainbow, on account of its various shades of colour. Digitalis (foxglove) is named from digitus, a finger, on account of the shape of its corolla, which is like the finger of a glove. Convallaria (lily of the valley) is named from a Latin word convallis, signifying, in the valley. Teucrium (germander) is named in honour of Teucer, a Trojan prince. The English 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 adjectives; generic names are nouns. The specific name sometimes indicates the number of leaves, as ORCHIS bifolia, (bifolia, signifies two leaves ;) or the colour of the corolla, as VIOLA tri-colour, (three-coloured violet ;) or the form of the root, as SOLANUM tuberosum, (with a tuberous root.) Specific names are often derived from the names of persons; thus a species of Origa num is named tournefortii, after its discoverer Tournefort.

The system of Linnæus may be illustrated by the following comparison ;-as.

Individual persons compose Families,

Families

Towns

Counties

Towns,

Counties,

"( States.

Orders

Genera,

Orders,

Classes.

Thus, as individual persons are the real existences which make up a state; so are individual plants the real existences which compose classes; the words town and county, genus and order, being general terms used to designate certain circumstances of these men and plants.

Natural Families.

After having analyzed a number of plants, you will begin to observe a striking resemblance in many genera, and your own minds will suggest the propriety of arranging them into groups, without any reference to the artificial class or order where they may have

* 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.

What is a genus ?-A knowledge of one species enables us to recognise all other species of the same genus-Derivations of generic names-Iris-Digitalis- Teucrium -Linnæa borealis-Specific names-Natural families.

been placed. We thus form natural families. If the whole vegetu. ble kingdom could thus be distributed into natural tribes, we should need no artificial system. But after selecting a few families, which exhibit striking marks of resemblance, we find genera whose reiation to other genera seems doubtful or obscure, and at length find a vast number of plants which seem to have few natural affinities with any other.

Among resemblances which gives rise to natural families, are, 1st, resemblance in seeds,

2d, in pericarps, or the envelopes of seeds,

3d, in stamens and pistils,

4th, in corollas and calyxes,

5th, in the modes of infloresence, or the manner in which the flowers grow together upon the stalks,

6th, in leaves,

7th, in roots and stems.

In order to form a correct idea of the natural methods of classification, it is necessary to observe many plants, and the most constant characters of their organs. To find the place of plants in the artificial classes and orders, it is only necessary to observe the distinctions of the stamens and pistils.

The physician is chiefly conversant with the natural characters of plants, especially with such as are connected by medicinal qualities; he considers one group as narcotics; another as tonics; another as stimulants, &c.)

The natural method depends for its utility, much upon the artificial system, which enables the student to ascertain the name of a plant, and thus learn its place among the natural orders. For example; suppose that a person meets with the plant commonly called stramonium, and wishes to know its character; by the Linnean System, he soon learns its botanical name, Datura; and this genus he finds belongs to the natural order, Solaneæ, characterized by qualities of an active and deleterious nature, as the Tobacco, Foxglove, &c.

The experienced botanist is not always obliged to refer to the artificial system for the natural character of an unknown plant. Being familiar with the characteristics of the different families, he can often determine at once by the habit or general appearance of the plant that it belongs to the lily tribe (Liliacea,) to the mallows tribe (Malvaceae,) to the wild turnip tribe (Aroidea,) or to any other of the conspicuous and well-defined natural orders or families.

To Linnæus belongs the honour of having first suggested the arrangement of plants into natural orders.

He published in 1738 what he modestly termed "Fragments of a natural method," consisting of 58 orders, founded upon the resemblance of plants in their habits, general appearance, or medicinal qualities.

The most popular Natural method is that of Jussieu, a botanist of Paris, improved by De Candolle of Geneva.* The characters employed in this method, are,

1. The structure of the Seed, with respect to cotyledons. A plant Professor Lindley of England, has recently published a work on the natural system, which is deservedly popular.

Resemblances which give rise to them-Physicians interested in the natural method -Connexion between the natural and artificial methods-Experienced botanists know plants by their habits-Natural method of Linnæus-Method of Jussieu-What are the characters employed in Jussieu's method?-How is the structure of the seed considered?

having no cotyledon is called, A-cotyledonous, with one, Mono-cotyɩedonous, and with two, Di-cotyledonous.

2. Insertion of the Stamens. The stamens are above the germ, under the germ, or around the germ; in the 1st case, they are Epi-gynous, 2d, Hypo-gynous, 3d, Peri-gynous.

3. Absence and presence of the Corolla. A-petalous, corolla wanting, Mono-petalous, corolla of one piece, Poly-petalous, many petals.

4. Union, or separation of Stamens and Pistils. Mono-ciinious, stamens and pistils on the same corollas, Di-clinous, stamens and pistils on different corollas.

5. Union or separation of anthers. Anthers distinct, or antheis combined.

These classes were at first formed of 100 orders; under the present modifications of Jussieu's method they have been multiplied, by establishing new orders from genera which seemed not to belong to any of the former established orders.

The acotyledons include the cryptogamous plants of Linnæus. They are also called cellulares, from their being formed of cellular tissue without a vascular system. These are by some botanists called flowerless plants ;* their leaves are destitute of veins. They have no seeds with cotyledons, but are reproduced from a powderlike substance, exhibiting nothing of the parts which constitute the seeds in the other divisions of the vegetable kingdom.

The monocotyledons, which consist principally of grasses, palms, and liliaceous plants, are endogenous as regards the structure of their stems and branches;-the veins in their leaves, instead of being reticulate, or spreading out in various directions like a net, are straight and parallel. This division consists of two large groups;-1st, plants whose flowers have petals, called Petalloide, as the iris and lily; the calyx and corolla being in three or six divisions ;-2d, where, instead of a proper calyx and corolla, the stamens and pistils are surrounded with glume-like bracts; these are called Glumaceœ ; as in the grasses.

The dicotyledons include all the phenogamous plants, except those which belong to the monocotyledonous division. These are vascular

It was long asserted by botanists, that every plant had a flower, although it might be invisible; but the term flowerless is now adopted by many for the cryptogamous family.

How the insertion of the stainens?-How is the corolla considered ?-How the anher?--Repeat the synopsis of Jussieu's method-What are the general characteris tics of acotyledons ?-Of monocotyledons ?-Of dicotyledons?

in their structure, exogenous in their mode of growth, and their leaves are distinguished by branching, reticulate veins.

Comparison of the Methods of Tournefort, Linnæus, and Jussieu.

We have now presented the pupil with the outlines of three modes of classification, exhibiting the plant under a variety of aspects, calculated to give general and extended views of the subject, and at the same time impress the mind with a few important distinctions.

Tournefort dwells chiefly on different aspects and circumstances of the corolla ;-Linnæus, of the stamens and pistils ;-Jussieu, of the cotyledons and insertion of the stamens.

Of the comparative merits of these methods, we would observe, that Tournefort's cannot be relied on, because the forms of corollas are often indefinite, and vary into each other; that of Jussieu ap pears too abstract to be used independently of the aid of some more simple method;-the number of cotyledons, though a definite and important character, cannot, in many cases, be determined without the slow process of waiting for the seeds to germinate ;-the insertion of stamens and of the corolla often appears doubtful, even to the experienced botanist. Much as this method has been admired, it is but little used; while, on the contrary, that of Linnæus has, for more than half a century, been regarded as the key to botanical knowledge.

The characters used in his 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 bellform, or funnel-form, there are many intermediate forms, which may be as much like one as the other. The insertion over the germ, or under the germ, are distinct, but the insertion around the germ sometimes blends with one, sometimes with the other mode. But between one or two stamens, or one or two pistils, there is no intermediate step, or gradual blending of distinctions, which leaves the student in doubt whether the case before him belongs to the one, or the other.

LECTURE XXII.

CHARACTERS USED IN CLASSIFICATION.'

LINNEUS, in his "Philosophy of Botany," established three kinds of characters to be used in the description of plants.

1st. Factitious (or made.) That which is, by agreement, taken as a mark of distinction; thus, certain circumstances with respect to stamens and pistils are fixed upon for distinguishing 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 peculiar 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 make a kind of arrangement of plants in their own minds, although they would find it

What is the use of considering different modes of classification ?-What is said of the comparative merits of the three methods which are mentioned ?--System of Linnæus offers something positive-Three kinds of characters to be used in descriptions of plants-Factitious character-Essential character--Natural.