The comparative quantities of fluid exhaled by the same plant at different times are regulated, not so much by temperature, as by the intensity of the light to which the leaves are exposed. It is only during the day, therefore, that this function is in activity. De Candolle has found that the artificial light of lamps produces on the leaves an effect similar to that of the solar rays, and in a degree proportionate to its intensity. As it is only through the stomata that exhalation proceeds, the number of these pores in a given surface must considerably influence the quantity of fluid exhaled. By the loss of so large a portion of the water, which in the rising sap had held in solution various foreign materials, these substances are rendered more disposed to separate from the fluid, and to become consolidated on the sides of the cells or vessels, to which they are conducted from the leaves. This, then, is the first modification in the qualities of the sap which it undergoes in those or gans. We may also discover, by the aid of the microscope, tha the fluids contained in these vessels are moving in cur rents with considerable rapidity, as appears from the visible motions of their globules; and they present, therefore, a remarkable analogy with the circulation of the blood in some of the inferior tribes of animals. This curious phenomenon was first observed by Schultz in the chilidonium, in the year 1820; and he designated it by the term cyclosis, in order to distinguish it from the real circulation, if, on further inquiry, it should be found entitled to the latter appellation. The circular movements which have been thus observed in the milky juices of plants, have lately attracted much attention among botanists; but considerable doubt still prevails whether these appearances afford sufficient evidence of the existence of a general circulation of nutrient juices in the vegetable systems of those plants which exhibit them; for it would appear that in reality the observed motions of the fluid are in every case partial, and the extent of the circuit very limited. The cause of these motions is not yet known; but probably they are ultimately referable to a vital contraction of the ves sels, for they cease the moment that the plant has received an injury, and are more active in proportion as the temperature of the atmosphere is higher. BOTANY. The sap having undergone in the leaves the double processes of exhalation and aëration, is thereby elaborated into a fluid corresponding to the blood of animals, and fitted for becoming incorporated with the vegetable organs. The crude fluid which enters the leaves is called the ascending sap; and after it leaves them, in order to be distributed throughout the plant, it has been called the returning sap. It still contains a considerable quantity of water, but a large proportion of that which has not been exhaled by the leaves, and its elements, oxygen and hydrogen, has combined with certain other substances, so Various eminent individuals have attempted the classias to form proximate vegetable products, of which gum fication and naming of plants, each of whose arrangeis the simplest, and generally the most abundant. The ments is called a system, and possesses certain peculiar returning sap descends from the leaves through two dif- features. The three systems which have been most ferent structures. In exogenous plants, the greater por- | esteemed, and wholly or partly adopted, are those of Tourtion finds a ready passage through the liber, or innermost nefort (1656—1708), Linnæus (1707—1778,) and Juslayer of bark, and another portion descends through the sieu (1699—1777). alburnum, or outermost layer of the wood. With regard to the exact channels through which it passes, the same degree of uncertainty prevails as with regard to those which transmit the ascending sap. De Candolle maintains, that in either case the fluids find their way through the intercellular spaces; other physiologists, however, are of opinion that particular vessels are appropriated to the office of transmitting the descending sap. The nature of the forces which actuate the sap in its descent from the leaves, and its distribution to different parts, as well as those powers which contribute to its motion from the roots to the leaves, are involved in equal obscurity. The hypothesis that it resulted from capillary attraction is now generally abandoned. SECRETION AND EXCRETION IN VEGETABLES. The modifications which the returning sap undergoes, and its conversion into gummy, saccharine, amylaceous, or ligneous products, are effected by the simpler kinds of cells. But there are other cellular organs in which greater changes take place in its nature, the agents for effecting which are unknown, and are therefore referred generally to the vital energies of vegetation. The process is termed secretion, and the organs by which it is conducted, glands. The matter secreted is sometimes retained in the cells, and sometimes appears on the outside as an excretion, for the plant has the power of throwing out by the root those superfluous or noxious matters which, if retained, would injure it. This explains the fact why plants render the soil where they have long been cultivated less suitable to their continuance in a vigorous condition than it originally was; and also why plants of a different species are frequently found to flourish very well in the same situation, where this apparent deterioration of the soil has taken place. The vessels in which the fluid secretions are contained are of a peculiar kind, and exhibit ramifications and junetions resembling those of the blood-vessels of animals. THE SYSTEM OF TOURNEFORT. Tournefort founded his system on the absence or presence, the figure, situation, and proportion, of the corolla. This part of the flower is always, when present, the most conspicuous and imposing, and attracted the notice of the earlier botanists, as it does that of children now, more than it really deserved; because, in fact, no part of the flower is more subject to incidental change than the corolla. He divided the vegetable kingdom into two principal parts, namely, herbs and trees; the primary divisions he subdivided into twenty-two classes, the first seventeen of which comprise the herbs, and the other five the ligneous vegetables; these are again separated into one hundred and nineteen sections, but without names or titles being applied to them, as in those of other botanists. The characters of the sections were not always sufficiently defined; and consequently the young botanist often met difficulties in arranging plants in their proper places. Though now known to be imperfect, the system of Tournefort possesses great merit. His labours, considering the state of the science when he lived, were indeed great, and far surpassing those of either Linnæus or Jussieu. In fact, Tournefort was pioneer to both, and amassed, and in many cases assorted to their hands, the materials of which both their systems are formed. THE LINNEAN, OR SEXUAL SYSTEM. The sexuality of plants had been discovered long before the time of Linnæus; but, as far as is now known, he was the first who suggested the idea of classifying plants according to the numbers, connection, and stations of the male and female organs. From the moment the idea occurred to him, he was indefatigable in the completion of a system which, no doubt, he fondly flattered himself was founded in nature. His great acquirements as a scholar, his love of natural history, his station among learned men, and his connection with many learned so cieties, uninently fitted him for achieving this great and laborious work. The plan of the Linnæan system of botany was intended to comprehend the whole vegetable kingdom, which was arranged in two grand divisions, namely, plants having visible flowers (Phænogamia), and plants having no visible flowers (Agamia or Cryp'ogamia). The whole are included in twenty-four classes; and these classes are subdivided into orders, genera, and species. The terms used to express the classes are compounded of the Greek numerals and the word andria, signifying man. These classes are subdivided into orders, which are designated from their number of pistils by Greek numerals also, with the addition of the word gynia, which siguifies Woman. The following is a summary of the distinguishing traits of the respective classes :— 1. Monandria, with one stamen-Marestail. 7. Heptandria, with seven stamens-Water plantain. 8. Octandria, with eight stamens-Heath. 9. Enneandria, with nine stamens-Flowering-rush. 10. Decandria, with ten stamens-Pink. are named as in the preceding classes; those having five pistils belong to the fifth order, or Pentagynia, and if they have many pistils, to the sixth order, or Polygynia. SIXTH CLASS, or Hexandria, having flowers with six stamens.-As they have one, two, or three pistils they belong to the first, second, or third orders; if they have six pistils, to the fourth order; and if many pistils to the fifth order. SEVENTH CLASS, or Heptandria, those having only seven stamens. If they have one or two pistils, they are classed as before; if four pistils, they belong to the third order; and if seven pistils, to the fourth order. EIGHTH CLASS, or Octandria, having flowers with only eight stamens.-If they have from one to four pistils, they rank in the order corresponding to the number. NINTH CLASS, or Enneandria, those having only nine stamens. If they have one pistil, they belong to the first order; if three, to the second; and if six, to the third. TENTH CLASS, or-Decandria, having only ten stamens. -If they have one, two, or three pistils, they belong to the first, second, or third orders; if five, to the fourth; and if ten, to the fifth order. Flowers with stamens of rather uncertain number, but of fixed insertion. ELEVENTH CLASS, or Podecandria, having flowers 11. Dodecandria, with eleven to nineteen stamens- -Agri- with from eleven to nineteen stamens inserted into the mony. receptacle.--If they have from one to five pistils they be12. Icosandria, twenty or more, inserted into the calyx— long to the orders corresponding to these numbers; and Rose. 13. Polyandria, twenty or more, inserted into the receptacle-Poppy. 14. Didynamia, two long and two short-Foxglove. 15. Tetradynamia, four long and two short-Wallflower. 16. Monadelphia, filaments combined in one set-Gera nium. 17. Diadelphia, filaments united into two sets-Pea. 18. Polyadelphia, filaments united into more than two sets-St. John's Wort. 19. Syngensia, anthers united into a tube, flowers compound-Thistle. 20. Gynandria, stamens situated upon the style, above the germen-Orchis. 21. Monacia, stamens and pistils in different flowers on the same plant-Spurge. 22. Diœcia, stamens and pistils in separate flowers on different plants-Willow. 23. Polygamia, stamens and pistils united or separate, on the same or on different plants, and having two different kinds of perianth-Orache. 24. Cryptogamia, stamens and pistils not visible-Moss. A more minute analysis of the system is as follows: Flowers with stamens of a fixed number, and equal in length. FIRST CLASS, or Monandria, having one stamen.-If they have one pistil, they are of the first order, or Monogynia; if two pistils, they are of the second order, or Digynia. SECOND CLASS, or Diandria, having two stamens.-If they have one pistil, they are of the first order, or Monogynia; if they have two pistils, they are of the second order, or Digynia; and if three, they are of the third order, or Trigynia. THIRD CLASS, or Triandria, having flowers with only three stamens.-If they have one pistil, they are of the first order; if two, they are of the second order, and if three, of the third order. if they have about twelve pistils, they belong to the sixth order. TWELFTH CLASS, or Icosandria, having flowers with twenty or more stamens inserted into the flower-cup or the blossom.--If they have one, two, or three pistils, they belong to the first, second, or third orders; if five, to the fourth order; and if many pistils, to the fifth order. THIRTEENTH CLASS, or Polyandria, those having flowers with from twenty to one hundred stamens inserted into the receptacle.-If they have from one to six pistils, they are classed as before; if they have many pistils, they belong to the seventh order. Flowers with two of the stamens shorter. FOURTEENTH CLASS, or Didynamia, having flowers with four stamens, two longer and two shorter, inserted on a one-petalled blossom.-If the four seeds appear not to be in a seed-vessel, they belong to the first order, or Gymnospermia; but if they appear to be concealed in a seed-organ, they belong to the second order, or Angiospermia. FIFTEENTH CLASS, or Tetradynamia, having flowers with six stamens, four longer and two shorter, the blossom with more petals than one.-If the seed-organ is a short pod, they belong to the first order, or Siliculosa; and if a long round pod, to the second order, or Siliquosa. Flowers with stamens united by their filaments. SIXTEENTH CLASS, or Monadelphia, having flowers with the filaments of all the stamens united at the base into one bundle.-If there are three stamens, they belong to the first order, Triandria; if five stamens, to the second order, Pentandria; if seven stamens, to the third order, Heptandria; if eight stamens, to the fourth order, Octandria; if ten stamens, to the fifth order, Decandria; if eleven stamens, to the sixth order, Endecandria; if from twelve to twenty stamens, to the seventh order, Dodecandria; and if more than twenty stamens, to the eighth order, Polyandria. FOURTH CLASS, or Tetrandria, having flowers with only four stamens equal in length.-If they have one pistil, SEVENTEENTH CLASS, or Diadelphia, having flowers they are of the first order; if two, of the second; three of with the filaments of all the stamens united into two the third; and if four, of the fourth order, or Tetragynia. bundles.-If they have five stamens, they belong to the FIFTH CLASS, or Pentandria, having flowers with on- first order, Pentandria; if six stamens, to the second ly five stamens.—Those having from one to four pistils, order, Hexandria; if eight stamens, to the third order, Octandria; and if ten stamens, to the fourth order, De- | imagine that the cabbage-palm (areca oleracia) and the candria. EIGHTEENTH CLASS, or Polyadelphia, having flowers with the filaments of all the stamens united into three or more bundles.-If there are from twelve to twentyfive stamens unconnected with the flower-cup, they belong to the first order, Dodecandria; if the bundled stamens are inserted in the cup, to the second order, Icosandria; and if there are more than twenty-five stamens unconnected with the flower-cup, to the third order, Polyandria. Flowers with stamens united by their anthers. NINETEENTH CLASS, or Heptandria, having flowers composite, with all the anthers in a floret united into a tube, whilst their filaments are not united. If all the florets are equal, they belong to the first order, Polygamia æqualis; if the florets of the circumference have pistils without stamens, to the second order, Polygamia superflua; if the florets of the circumference have neither stamens nor pistils, to the third order, Polygamia frustranea; if the florets of the circumference have pistils without stamens, and those of the centre stamens without pistils, to the fourth order, Polygamia necessaria; and if the florets have a partial flower-cup all within a general flower-cup, to the fifth order, Polygamia segregata. Flowers with the stamens and pistils united. TWENTIETH CLASS, or Gynandria, having flowers with the stamens inserted upon the style or seed-organ. If they have one stamen, they belong to the first order, Monandria; if two stamens, to the second order, Diandria; if three stamens, to the third order, Triandria; if four stamens, to the fourth order, Tetrandria; if five stamens, to the fifth order, Pentandria; if six stamens, to the sixth order, Hexandria; and if eight stamens, to the eighth order, Octandria. Flowers of only one sex. TWENTY-FIRST CLASS, or Monoecia, having flowers, some with pistils only, and some with stamens only, on the same plant. There are nine orders, taken from the number and bundling of the stamens, as before. TWENTY-SECOND CLASS, or Diccia, having flowers with pistils only, or with stamens only, on two separate plants of the same species. There are nine orders, founded as in the preceding class. TWENTY-THIRD CLASS, or Polygamia, having flowers with both stamens and pistils, and also with only one of these, both on the same and on separate plants of the same species. There are three orders. No flowers apparent on the plants. TWENTY-FOURTH CLASS, or Cryptogamia. Stamens and pistils, if present, cannot, from being very minute, be ascertained. The class contains five orders-Ferns, Filices; Mosses, Musci; Liverworts, Hepatica; Seaweeds, Alga and the Mushrooms, Fungi. To these Linnæus added another class, or rather appendix, which he called Palma, the flowers of which were not sufficiently known in his time to admit of their being properly placed in the system. They are now distributed into the various classes and orders of the sexual system. they are still kept separate by Jussieu, who has, as Linnæus did, arranged them into an order by them selves, under the old name. In fact, the genus Palma is of all others the least associable with the Linnæan plan of arrangement; being as distinct a tribe of plants in their structure, forms, and manner of growth, as can be found in the whole vegetable kingdom. Still there were stations provided for them in the sexual scheme, where they have been placed by late writers; but, as already observed, they do not associate well with the genera mong which they are ranked. For instance, who would Scotch pine (pinus sylvestris) were any way allied to each other? Yet the Linnæan botanist must unite them, because their flowers are respectively monacious, and their stamens are united in one brotherhood. On THE JUSSIEUIAN, OR NATURAL SYSTEM. The author of this new system of botany has taken a very comprehensive view of the vegetable kingdom, and has been fortunate in fixing on those greater characteristics of plants which distinguish them from each other, and which at the same time are the least variable. examining closely the vegetable membrane, he found it was either uniformly simple, that is, consisting of tissues of cells of nearly equal size and consistence, or of tissues of which the cells were of various sizes intermixed with each other, and formed into fibres lying in straight or in spiral positions, and forming tubes and openings of different structure and consistence. This evident difference of structure served to divide the vegetable kingdom into two parts; the first he called Cellulares or Acotyledonee, that is, plants formed wholly of cellular membrane, and rising from their seeds, or sporules, destitute of cotyledons or seed-leaves. Among these Acotyledoneæ are embraced the lower grades of the vegetable creation-the Filices, the Musci, the Hepatica, the Alge, the Fungibeing placed, as it were, at the bottom of the scale, and exhibiting, in their outward aspect as well as in their internal structure, nothing of that loveliness of form, and but rarely that brilliancy of colouring, by which some of the other divisions of plants are distinguished. They are the first and rudest types of vegetable life, many of them consisting merely of a cluster of minute cells, or of minute threads, as in the case of proto-coccus and byssus; and many of them being, in fact, nothing more than a these minute and apparently insignificant tribes of vege mere slime or mucus, as in the moulds and nostors. Yet tables, as already stated, are by no means useless or su perfluous in the scale of nature. Germination of Dicotyledonous and Monocotyledonous Plants. The plants composed of the second description of membrane, Jussieu named Vasculares or Coʻyledonea, because the organization was more complicated, consisting of cells of various size, lying in various positions, in denser or looser laminæ or partitions, and being invariably fibrous; and, moreover, rising from their seeds furnished with cotyledons or seed-leaves. Of these, some presented one seed-leaf only, but the great majority presented two; hence the latter were called Dicotyledones, and the former Monocotyledonea. This difference in the development of the seedlings of Vasculares, served as a basis for the two classes into which it is divided and named, as above stated. But besides the difference in the germination of vas cular plants, they also differ materially in the manner of their growth. The first class, Dicotyledonea, is annually increased in bulk by additions of bark and wood on the outside, hence it is also called Exogenes; whereas the second class, Monocotyledonea, is enlarged by the expansion of the interior parts of the stem, and therefore is also called Endogenes. These are very striking charac teristics of the two classes, as regards their manner of growth; but there is another very obvious distinction not only in the structure of their stems, but in t Dicotyledonous Leaf of the common Apple-tree. By these obvious distinctions in the manner of the germination of the seeds, the modes of accretion, and in the structure of the stems and foliage, the two classes of Cotyledonea, or vascular plants, are clearly marked. But as there are great differences with respect to the stations, connections, and numbers of the floral members of the plants included in this first division, the author of the system found it expedient, in order to facilitate the study of the science, to separate it, as already stated, into two classes; namely, Dicotyledonea and Monocotyledoned; the former being again separated into two subdivisions, namely, Dichlamydea, that is, plants whose flowers have two coats or coverings, the calyx and corolla being distinct; and Monochlamydea, that is, plants whose flowers have one coat or covering, the calyx and corolla not being distinct, but blended in one, as exemplified in those of the mezereon. Monocotyledonous Leaf of the Gloriosa Superba. In so limited a treatise it would be impossible, even were it desirable, to mention all the features and characteristics of the Jussieuian system, as comprehended in its ramified divisions, subdivisions, orders, genera, and species; and, indeed, to acquire any thing like useful knowledge on the subject, it must be studied practically in the garden and fields, under the instructions of a master. It is generally allowed that the minute complexity of the subdivisions and orders is most perplexing to the pupil, and a simplification in this respect, as well as in the harshness of the nomenclature, would be very desi rable. It is well known that there are many genera which stand on the confines of two orders, with neither of which they exactly agree. In such cases, uniting the neutral with one or other of the more decidedly marked orders, would surely be better than constituting a new order, merely for the purpose of more completely or scientifically identifying one unsociable plant. It appears that Jussieu himself was strongly impressed with the desire of limiting the number of his orders, as well as the genera; nevertheless, almost all the improvements which have been recently made in the system by his followers, are divisions of orders, and subdivisions of genera, thus expanding rather than simplifying the system. It cannot be denied, however, that there are many persons engaged in the cultivation of plants who would rejoice at seeing a new scheme of scientific botany by which the orders of the natural system would be reduced, and the number of genera diminished. Such a thing is not so impracticable as may be imagined; a master mind to contrive, and a few talented practical botanists to sanction the scheme, and fix the nomenclature, would be a work well worth the attention and labours of some universal botanical society instituted for this special purpose. Botany, as well as every other science, has lately been greatly advanced by that friendly and highly commendable intercourse and interchange of social and scientific communion between home and foreign professors; and no doubt, whatever may be its defects, a union an ong Jits professors will speedily supply a remedy. NATURAL THEOLOGY. NATURAL THEOLOGY is that branch of logical science which comprehends the discovery of the existence and ttributes of a Creator, by investigating the evidences of Jesign in the works of the creation; and, in an enlarged sense, it refers to the probable intentions of God with regard to his creatures, their duty, and conduct. It cannot but appear to every rational mind, that a subject involving such important views and considerations is full of the deepest interest, and may be made the agent of much intellectual improvement. It is incumbent on us to read the wisdom of God, and his admirable contrivance, in all that we see around us and above us, and which pertains to the universe to which we belong. Independently of the pleasure, and perhaps worldly advantage, which the study of Natural Theology will produce, it will be equally serviceable in keeping alive feelings of piety and devotion. As Lord Brougham has property remarked, "even the inspired penmen have constant recourse to the views which are derived from the contemplation of nature when they would exalt the Deity by a description of his attributes, or inculcate sentiments of devotion towards him. How excellent,' says the Psalmist, is thy name in all the earth! thou hast set thy glory above the heavens. I will consider the heavens, the work of thy fingers; the moon and stars which thou hast ordained.'" of the conveniences of civilized life; or were the furniture, the weapons, or the instruments in and around them, such as barbarous nations generally use, we might rea sonably argue that we had found the dwelling of an untamed savage. But if, instead of this, we find the sur rounding land trenched, enclosed, and cultivated; should we find the common articles of European husbandry, and the common utensils of an European household, we should naturally draw the inference that we had reached the abode of an emigrant, who had thus reared around him the attributes of civilized life. Much more a few additional observations might reveal to us, and enable us to form conjectures, bearing the aspect of probability, concerning the people among whom we had fallen. Now, it is in this way alone that we can argue respecting the Author of all things, and discover proofs and demonstrations of a first supreme Cause. To prove that the formation of all things was the result of DESIGN, it is only necessary to show that they are in general, or in so far as we can discover, admirably suited to the uses and purposes to which they are to be applied that their arrangement is perfectly harmonious-and that it is impossible that any chance could have thrown them together in a way so happy. To discover if this design can be evidenced or demonstrated, it is necessary to seek through the various works of creation with which we are surrounded; and the more minute we make our inspection, the more likely shall we be to perceive the deduction. If there be some departments to which our senses have a readier access than to others, and which we can therefore more readily examine, from these especially we ought to deduce our results. It may be that we shall find many things, which, from the deficiency of our observing faculties, we cannot understand, nor discover the uses or consequent design which they display, but still, if, in the course of our inspection, we find every part admirably adapted for a specific purpose, and teeming with the most convincing evidences of design, then we may with safety and true philosophy infer that in those objects, which, from their nature and our imperfection we cannot so completely investigate, a greater degree of light would tend to confirm the result to which our previous observations, among other things, had led It is worthy of remark, as showing the depth and solidity of the foundation on which rests the existence of a supreme, intelligent, and beneficent First Cause, that the farther we push our discoveries, the more clearly are the Divine perfections exhibited. It is not merely true that, on a superficial view, we perceive the necessity of believing that a limited and changing world, such as that on which we dwell, could neither exist without being produced, nor be the author of its own existence; and that there must, therefore, be, beyond the range of our senses, an independent and uncreated Essence, without beginning, without bounds, incapable of change, intelligent, ever-active, all-pervading; but it is also certain, that those views are not only uncontradicted, but fully established by the most minute survey of the objects within the sphere of our vision; so that he who penetrates the deepest into the secrets of nature, only multiplies proofs of that most sublime and most animating us. truth, that verily there is a God" who made and rules the universe. It is difficult to understand that strange moral obtuseness which has induced a certain class of writers to reject this; for grant but one assertion, which 18-and it is not easily to be questioned—that there exist in nature indisputable traces of design, planned with wisdom, directed by goodness, and accomplished by power, and it follows that there also of necessity must have been a wise, a good, and a powerful Designer. Let us suppose ourselves cast ashore upon some island previously unknown to us; we immediately proceed to examine the appearances which present themselves, in order to discover if any traces exist of human inhabitants, To ascertain if such beings there existed, it would not be necessary that they should actually be seen by us. In our wanderings we might come upon a hut bearing all the marks of occupation; we might see the roots of the trees which had been felled to form it, and other tokens of the recent presence of man upon the spot; and did we desire to discover something of their character and habits before we presented ourselves to their notice, it is ⚫ most probable that sufficient data would be also affor ed on which to found an opinion. Were the habitations we discovered merely wigwams, or rude enclosures destitute 190 DESIGN IN THE PLANETARY SYSTEM. To the uninstructed eye, the earth which we inhabit appears on a clear night to be surrounded by a numerous host of radiant points, which, rising in the east, move majestically through the sky until they reach the western horizon, when they set or disappear; and so completely does this idea commend itself to the mind of an observer, that it requires a considerable effort to conceive how it can be otherwise. But science has taught us that this is a mere illusion, and the discoveries of Copernicus and Sir Isaac Newton have established the truth suggested by Pythagoras upwards of 2000 years before the time of either of them, that the apparent mo tion of the heavens is the consequence of the real revolu tion of the earth every twenty-four hours upon its axis; that, with relation to the earth, the sun is stationary, while the earth every year completes a journey round him; that the planets are globes similar to our own, revolving at once upon their own axis, and round the sun; that the moon is a satellite or attendant upon the earth, accompanying it in its course, and at the same time describing every month a circular orbit round it; and that to several of the planets are attached similar |