1. Comparison of organs. In order to ascertain the relative importance of the organs, it is necessary to compare them in reference to their functions. We say, for instance, that the brain holds a higher rank than the nerves, and the heart than the veins, but this does not decide the relative rank of the brain and heart. Or, to adduce an illustration of a different kind, a general is higher than a captain, and a governor of a province than the mayor of a town, but the arbitrary laws of etiquette alone decide, whether the general or governor be entitled to precedence. The first general principle in the classification of organized beings is, that the importance of each organ can be calculated only when compared with those organs, which relate to the same class of functions. In the vegetable organization there are two classes of functions, one destined to the preservation of the individual, the other to that of the species. These, no doubt, are of equal importance, and always possess corresponding degrees of perfection. Hence, we deduce another general principle of classification, viz. that systems, established upon either of these two grand classes of functions, would be equally natural, provided they were constructed with the same care. The preference, indeed, has been usually given to the reproductive organs, because differences in the vegetable organ zation are more perceptible in them than in the nutritive organs, and more especially too, because the latter have been comparatively but little studied. Were they both equally well understood, without doubt a system founded on one, would be identical with one established on the other; for every thing leads us to believe, that any complication, or other modification in one class of functions, is attended by a similar one in the other. Cesalpinus had established certain classes upon the structure of the embryo alone, many centuries before Desfontaines was conducted to the same result by making use of the nutritive organs. Hence also we make the division of plants into Monocotyledons and Dicotyledons with so much the more confidence, because we are equally led to it, whether we assume as the basis of our reasonings, the reproductive or nutritive organs. In order to estimate the importance of each organ in a given function, we must ascertain what is essential to its performance, when reduced to its simplest conditions. Thus, the essential part of reproduction is fecundation, and the fecundating organs are con

sequently of higher importance than all their envelopes. At first, the sexual organs are equally indispensable, but the duty of the male parts is of short continuance, and they, together with a portion of the female parts, are destroyed after fecundation. But as the female organ, beside this short-lived part, includes another for which all the rest are constructed, its importance is obviously greater than that of the male. Again: in the part of the female organ that remains, the integuments or fruit may be separated from the seed, and exist but for it. The seed has thus a higher value than its envelopes; and continuing the same reasoning, we at last find the embryo performing the most important part in the whole function of reproduction. If, now, our conclusions be just, the organs may be arranged, in regard to their relative importance, in the following order. 1. The embryo, the great end of all the rest. 2. The sexual organs, which are only the means. 3. The envelopes of the embryo, viz. the integuments of the seed and the pericarp. 4. The envelopes of the sexual organs, viz. the corolla, calyx and involucre. 5. The nectaries and other accessory organs. Another means of judging of the relative importance of organs, is by the degree of constancy with which they appear in the vegetable organization. Some, we know, are frequently absent, some, not so often, while others are almost always present. Hence we infer, that the stamens and pistils have a higher rank than the calyx and corolla, and these latter than the nectaries; the filaments of the stamen and pistil are thus shown to be of less consequence, than the anthers and stigmas.

A third means of judging is, to observe to what point a given organ is more or less intimately connected with the structure of certain groups, already acknowledged by naturalists. Thus, we conclude that stipules are more important than spines, because a great number of families either have or have not stipules, while there are many in which we find indifferently species with or without spines.

II. The circumstances that may deceive the observer as to the true nature of the organs. Before we can decide any question as to the relative importance of the organs, we need some means of distinguishing the organs themselves, and recognising their true nature, under all the modifications they are liable to experience. Looking at a single organ abstracted from the general structure, we can judge of its nature solely by its use,

whatever may be its position, form, or mode of action; thus, the organ of vision is called the eye, and the part that bears the flower is called the peduncle. But when we examine beings as a whole, and judge of the nature of the organs in reference to the symmetrical plan on which they are constructed, this method will lead us into grievous errors. The tail of the kangaroo serves the animal as a leg, yet nobody denies that it is still a tail; the nose of the elephant, prolonged to a great length, performs the office of a true hand; and the teeth implanted in the incisive bone, serve a purpose entirely foreign to mastication, yet none pretend to dispute the anatomical analogy of these organs with the nose and teeth of other mammifers. So too, we see the leaves of plants sometimes prolonged and changed into tendrils for the purpose of supporting the stem, though their primitive function is to elaborate the nutritious juices. The stipules, the peduncles, and even the lobes of the corolla may be converted to the same use, and every body is familiar with the leafy appearance and structure of the branches of the Indian Fig, or Prickly Pear, (Cactus Opuntia). From these examples and a host more that we might mention, we deduce the general conclusion, that it frequently happens, in consequence of a given system of structure, that a certain function, not being sufficiently performed by the organ ordinarily allotted to it, is discharged wholly or in part by another. It is this system of organization, this symmetry of the organs as compared with one another, of which a knowledge is essentially necessary to a perception of the general harmony and natural classification of beings. This symmetry of parts, which should be a prominent object of the naturalist's studies, is, in one word, the result of their relative disposition; and therefore, whenever this disposition is the same, no matter how various may be the form of particular organs in other respects, the subjects present a kind of general resemblance, that strikes the least practised eye.

Among the causes of error that are liable to mislead us in ascertaining the true nature of the organs, the principal is abortion, more or less complete, which alters their symmetry. Every body knows, that sometimes certain parts of organized beings do not receive that increase and development for which they were evidently destined, owing either to the compression of a foreign body, or a loss of part of their nourishment.

This

effect may be produced by internal causes, such as caries, for instance, as well as external; but among those which prevent certain organs from receiving their full increase, it is possible that some may be the necessary consequences of the growth of another part, and will, of course, constantly occur in a given system of organization. We may, therefore, admit in theory the constant and predisposed abortion of certain organs, either wholly or in part. This is a startling doctrine to those yet uninitiated into a knowledge of the more hidden laws of organization, but is, nevertheless, as easy of proof as an abundance of the clearest facts can make it. Whoever will take the trouble to cut across the ovary of a horse-chestnut flower, soon after the petals have fallen, will find three cells and two seeds in each cell; but let him look a few weeks afterwards, when the fruit has attained its perfect growth, and three seeds or nuts are the most that can ever be found,sometimes but one. But to remove all doubt as to the fact and nature of this phenomenon, we have only to cut open an ovary every day after the period of flowering, to see some of the seeds gradually increasing, while the others are observed to remain stationary, and finally to be completely choked by the development of the first. Now, when we bear in mind that this phenomenon is constant and takes place in trees perfectly sound, are we not forced to believe, that it is owing to some circumstance in the very system of the organization of this tree? In the oak, too, we have another familiar instance of a three-celled and six-seeded ovary finally resulting in one perfect seed only. The disappearance of the sexual organs is a very common occurrence, of which an example may be witnessed in the marginal florets of the snow-ball genus, and many other plants whose flowers grow together in large masses. The question then recurs, how shall we recognise the general symmetry of plants, amid the confusion produced by these partial abortions? Some light may be obtained on this point from observing appearances denominated monstrous,-an epithet commonly given to all such as differ from the habitual state of the organs, though many of them are returns of nature to the symmetrical order. Thus, to recur to an example already cited, if, by some accidental cause, the six little seeds of the horse-chestnut or oak should obtain their full growth, and present us with a fruit of six nuts or acorns, we should call it monstrous, while, in truth, it is the single-seeded fruit

that is the real monster. The Antirrhinum or Toad-flax has a personate corolla, the lower segment of which sends out a long spur, with four stamens of unequal length, and the rudiment of a fifth. In a variety of this plant called Peloria, the flower is perfectly regular, having an equal fivelobed corolla sending out five equidistant spurs, in which are five equal stamens. Here is a most singular case of a return of nature to her favorite symmetry, and no doubt can be left as to which is the real monster. The rare example of certain compound flowers, where we see the egret become leafy and assume the appearance of a true calyx, is a strong proof of the egret's being, in fact, an abortive calyx. It is well known also, that trees which have spinous branches in a dry soil, cease to have them in a fertile one,-a sufficient proof that spines are abortive branches.

Another guide, less sure perhaps, but adapted to more general use, is analogy or induction. It is found solely in a knowledge of the respective positions of organs. In an Albuca, for instance, we find the entire structure of a liliaceous plant, excepting that it has only three stamens bearing anthers, while between them we observe three filaments placed precisely where stamens would be, and very similar to the existing stamens. Hence, we conclude that these filaments are abortive stamens. In the Ice-plant (Mesembryanthemum,) we find a great number of filaments disposed in several ranks, but all adhering by their bases, and attached to the same point of the calyx, the interior bearing fertile anthers, the middle having the anthers wholly or in part abortive, and the exterior being true petals. We conclude then, that in this genus, the petals are naturally abortive stamens, and from a crowd of similar facts we are led by a very powerful analogy to the belief, that the petals of all plants, as a general theorem, are only filaments of stamens, whose development is in the relation of cause or effect to the abortion of the anther. When too we see the calyx of a Valerian or Scabious evidently assuming the form of an egret or pappus, we are induced by analogy to extend this result to the compound flowers, and conclude that their pappus is only an abortive calyx. Finally, by analogy alone, we judge in a host of cases of the natural number of the parts of flowers and fruits, and are led to look carefully for those whose abortion we suspect. It is the successful use of this principle which, more than any thing else, facilitates the