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 appears 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.

very difficult to explain their reasons for this classification to others. It will appear, from this definition of natural characters, that in some respects, the method of Jussieu is no less artificial than that of · Linnæus, since it depends upon particulars which can only be learned and understood by the aid of science; and we must admit that the genera which its orders exhibit, are often as unlike, in habit and properties, as are those which compose the classes of Linnæus. 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 selecting by natural characters, nutritious substances, and avoiding 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 an instinct given them by this same Almighty Benefactor.

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 infloresence; Leguminous, from the nature of the fruit. In many cases the family takes its name from a conspicuous genus belonging to it; as the Rosacea, or rose-like plants; Papaveracea, or poppy tribe, from Papaver, the poppy.

Natural families or orders resemble artificial orders in being composed of genera, but the principles on which these are brought together differ widely in the two cases.

In the truly 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 afterward the seed, branch out from one common centre, like the sticks of an umbrella; this general resemblance being observable by all, it seems very natural to class such plants together,

But in the artificial orders, genera which may be very unlike in other respects, are brought together, from the single circumstance of plants having the same number of stamens and pistils. Thus, in the first order of the eighth class, we have the tulip and the bulrush, the lily of the valley and the sweet flag. In the second order of the fifth 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

Why is the method of Jussieu no less artificial than that of Linnæus ?--Animals distinguished by natural characters-Savages distinguish plants by these characters-Animals capable of discerning these natural characters-What gives name to a natural family of plants ?-In what respect do natural families resemble artificial orders? How do they differ ?-Why may natural families be formed without a knowledge of botany?-Genera in the artificial orders brought together by having the same number of stamens and pistils.

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 may be compared to a dictionary; though by its use we do not at first find the name 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 with these as our guide, we proceed to find the name. Having ascertained the botanical name, we can easily find to what natural family a plant belongs, and thus learn its habits, medicinal use, and other important particulars. The natural method may be considered as the grammar of botany; for between this, and the artificial system, the same relation exists, as between the grammar and dictionary of a language; it would be idle to attempt to decide on their comparative merits, since both are essential to science.

As the subject of classification is so important to a knowledge of botanical science, we will now consider the general principles on which it depends.

Rules.

1st. All botanical classification results from an examination and comparison of plants.

2d. Every organic distinction which establishes between individuals 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, its different modification and its absence, are so many characters.

4th. The presence of an organ furnishes positive characters, its absence negative characters.

Positive characters offering means of comparison, show 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 particulars where visible and striking resemblances may be observed; 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 polypetalous corollas, this single character establishes, at once, the difference, which exists between the two groups, and the resemblance, which exists between individuals of each group. Thus positive characters possess a great advantage over negative ones; the latter should never be employed

Artificial system of arrangement compared to a dictionary-First learn the charac ters, then the name-The natural method considered as the grammar of botanyMention the first four rules which are given for classification-Positive and negative characters-Give illustrations of these characters, with their uses-Advantage of positive characters over negative.

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.

But

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. 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. 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 characteristic 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 important 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 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 reproduction. Labiate and caryophyllous plants agree in having their leaves opposite, and yet there is no resemblance in their flow

ers.

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 characters 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.

In separating or bringing together plants, we should, as far as possible, 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 discovered by such aid, it is

That is, two long and two short stamens.

Positive characters founded only upon evident facts-What is the fifth rule ?--The sixth? 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?

necessary to resort to this instrument, in order to establish the natural relations of plants.*

Having considered the meaning of individual, species, genus, and family, and of the characteristics by which these are grouped together, let us take a general view of the subject. It is evident, by the formation of species, genera, and families, that every species should offer the essential characters of the family and genus to which it belongs; while the marks which distinguish this species from another species of its genus, will be such as do not belong to the whole genus or family. The different genera in families are also distinguished by characters which do not belong to the whole family; every individual, then, will possess its specific character, its generic character, and its family character.

The specific character is less important than the generic, as it is mostly founded on the characters of the organs of vegetation, which we have seen are isolated, and less important than the coexistent characters. We often find, in the analysis of plants, a great difficulty in determining their species, from the want of definite marks of distinction.

Generic characters are mostly of the coexistent kind, and are more valuable than the specific characters. The distinctions of genera are usually much more apparent than those of species; as a rose can be more easily distinguished from a pink, than one species of rose from another species.

Families are grouped together by marks of resemblance found in genera. These family characters are, of all others, the most important. In the artificial classes and orders we depend on what we have before termed factitious characters. In species, genera, and families, the essential characters are also natural characters.

LECTURE XXIII.

USE OF BOTANICAL NAMES-ARTIFICIAL CLASSES AND ORDERS CONSIDERED IN GROUPS-CLASSES MONANDRIA AND DIANDRIA.

You have been taught the principles on which the Linnæan system is founded; we shall now examine each class separately, with the orders it contains, and the most remarkable plants and natural families which we shall meet with in our progress through this system. We have observed, that this appears to be the best method yet discovered of classing new plants, and of ascertaining the botanical names of those which are already known by common names. If, in all countries, the common names were alike, there would be no need of any other; but the names of plants vary in different languages as much as other terms. Even in the same country, and often in the same neighbourhood, the common names of plants are different; but botanical names are the same, in all ages and coun

The foregoing rules and observations respecting characters for classification, are chiefly translated from Mirbel's "Elemens de Botanique."

General view of the subject of classification-Which is the more important, the specific or generic character?-Why are generic characters most valuable ?-How are families grouped together?-On what do artificial orders depend?-What are the essential characters in species, genera, and families?-Why are not the common names of plants sufficient for all purposes?