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have the power of releasing their little prisoner. This is the singular structure of Aristolochia Clematitis, (Common Birthwort,) a native of Britain.

• The corolla of this flower, which is tubular, but terminating up i wards in a ligulate limb, is inflated into a globular figure at the base. The tubular part is internally beset with stiff hairs pointing downwards. The globular part contains the pistil, which consists merely of a germen and stigma, together with the surrounding stamens. But the stanens being shorter than even the germen, cannot dis- ! charge the pollen so as to throw it upon the stigma, as the flower stands always upright till after impregnation. And hence without some additional and peculiar aid, the pollen must necessarily fall down to the bottom of the flower. Now the aid that nature has furnished in this case, is that of the agency of the Tipula pernicor. nis, a small insect, which entering the tube of the corolla in quest of honey, descends to the bottom, and rummages about till it becomes quite covered with pollen; but not being able to force its way out again, owing to the downward position of the hairs, which converge to a point like the wires of a mouse trap, and being somewhat impatient of its confinement, it brushes backwards and forwards, trying every corner, till after repeatedly traversing the stigma, it covers it with pollen sufficient for its impregnation; in consequence of which, the flower soon begins to droop, and the hairs to shrink to the side of the lube, effecting an easy plissage for the escape of the insect.' Vol. II. pp. 353, 351.

None of the investigations of the physiological botanist appear to be more difficult and intricate, than those which are directed to the explanation of the excitability of the vegetable structure. In some cases, as we have seen, mere contact with the glandular hairs, or irritable membrane of the plant, is a sufficient stimulus for the production of the most striking phenomena. These cases appear to approach most nearly to the nervous action upon the animal system, and would almost induce us to believe that vegetables are endued witla sensation as well as vitality. In by far the greater number of instances of vegetable susceptibility, the immediate exciting cause is light, or temperature, or humidity : these stimulate the plant in proportion to their degrees of intensity. Here, the manner of action is either chemical, or mechanical, and is much more conformable to the changes produced in uporganized matter when operated upon by similar circumstances. Temperature and humidity doubtless produce their effects chiefly in a mechanical way, by the various degrees of tension or relaxation of the vegetable fibre. The presence or

. absence of light, combined with the above-mentioned causes, is productive of a great number of phenomena principally to be referred to chemical agency. During the darkness of the night, the numerous tribes of plants, as well as of animals, sink into repose. The great Linnæus has even ventured to trace the

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analogy further, and to assert that vegetables sleep! Whatever be the real nature of the changes which they undergo, certain it is that, during the night, the functions of plants are, in some species, materially different from those which they perform during the day, and in others are totally suspended. While the sun is above the horizon, carbonic acid gas is inhaled by the vegetable, and oxygen gas is evolved. When the light has departed, a precisely contrary elaboration of these two gases commences; the carbonic being given out, and oxygene taken in. As soon as the dews of the evening begin to fall, a universal change takes place throughout the vegetable world. The flower hangs its head, as if pensively awaiting the return of the holy

light” which no longer sheds its genial influence; the corolla closes, as if unwilling to expand its delicate structure to ke illuminated by no sun-beam, and to be painted by no ray of heaven. Even the leaves appear to sympathize in the gloom which prevails over the face of nature; those of many species folding themselves back upon the stalk, or drooping till the return of day! Such are the analogies between the vegetable and animal creation, which not only poets, but philosophers delight in tracing. To call this alteration or suspension of vegetable functions, their sleep, is doubtless to assume that they are sentient, and is to give a plausible name to a phenomenon, the rationale of which is but ill understood. If, however, the analogy be fancifal, it is innocent; it is scarcely possible that it should mislead ; and it conducts us to a more extended observaion of an order of facts both important and interesting.

Analogies between the condition of the merely organized and he intellectual world, have been traced not only in their funcions, but in accidental circumstances with which they are conjected. Our readers may, perhaps, smile when we tell them bat, if men have clocks, so bave flowers :

* Although many plants open their fowers in the morning and shut hem again in the evening, yet all flowers do not open and shut at the ame time. Plants of the same species, are, however, pretty, regular o an hour, other circumstances being the same; and hence the daily pening and shutting of the flower has been denominated by botanists, he Horologium Flore. Flowers requiring but a slight application of timulus open early in the morning, while others requiring more, pen somewhat later. Some do not open till noon, and some, whose xtreme delicacy cannot bear the action of light at all, open only at ight, such as the Cactus grandiflora, or night-blowing Cereus.' I. p. 445.

We have vegetable weather-gages also, and of very delicate ructure. That the changes in the state of the atmosphere are dicated by corresponding

effects in the habits of certain plants, a fact which suggests itself to the notice of the most trivial

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observer. Indeed, some of the most sensible of our philosophi. cal instruments bave been constructed upon this very principle. The bygrometer is an instance in point. The most delicate of these instruments, is that which has been constructed by Major Kater, froin the beard of an Indian grass, the Andropogon eontortum (twisted' Andropogon), which, from its zero of perfect dryness, to the saturation by moisture, twists around its own axis ten or twelve times :* if, therefore, one end of the beard be fixed, and the other be attached to an index pointing to a circumference divided into one hundred equal parts, we have the enormous scale of 1000 or 1200 degrees. Human skill, bow. ever, is not absolutely necessary to the existence of a vegetable weather-gage; and yet we can scarcely subscribe implicitly to all the followiog assertions :

• The opening or shutting of some flowers, depends not so much on the action of the stimulus of light, as on the existing state of the atmosphere, and hence their opening or shutting betokens change. If the Siberian Sow-thistle [Sonchus Sibiricus+] shuts at night, the ensuing day will be fine; and if it opens it will be cloudy and rainy. If the African Marigold [Tagetes erecta) shuts after seven o'clock in the morning, rain is near at hand. And if the Convolvulus arvensis [the Corn Bind-weed,] Calendula fluviatilis [C. pluvialis ? we presume the Small Cape Marygold,] or Anagallis arvensis [the Scarlet Pimpernell,] are even already open, they will shut upon the approach of rain, the last of which, from its peculiar susceptibility, has obtained the Dame of the Poor Man's Weather-glass. Vol. II. p.416.

If we were inclined to pursue these accidental analogies, between the productions of art and the spontaneous results of unassisted nature, we might amuse, our readers with a thousand popular examples. Dionæa muscipulu (Vepus's Fly-trap) has been before quoted; this curious plant is not only an example of irritability analogous to the nervous affections of animated beings, but the very machinery by which it entraps the uuwary fly, bears a striking similarity to a rat-trap. The North American Saracenia purpurea (the Purple side saddle flower) bas its leaves furnished with an anomalous appendage somewhat funnelshaped, forming an artificial bucket adapted to contain water. Nepenthes distillatoria (the Ceylon Pitcher-plant) is still more sportively imitative. From the end of the leaf issues a slender

* See an interesting memoir on the hygrometric properties of this curious, plant (the Oobeena Hoolou of the Mysore country) in the Asiatic Researches, Vol. 18. It was first brought to England in 1806; but the mechanical construction of the instrument has been much improved by Mr. Jones, Optician, Charing Cross. Rev.

+ Throughout this article, wherever either the Scientific or the Trivial name has been omitted by our author, we have inserted it Rev.

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edicle from which hangs a vegetable Pitcher, filled with limpid vater; and the mouth of this natural amphora is furnished with i membranaceous lil or calyptra, opening on one side! Sowe criters bave fancifully imagined that a vegetable compass exists.

the structure of the concentric layers in the horizontal section of the trunks of trees. It has been urged that these do not? trictly conforın to the axis, the excess being attributed to the creater action of the sun on that part of the trunk which faces ... he meridian. This effect has been thought, to be sufficiently striking and uniform to serve as a sort of compass, sy which the bewildered traveller might safely steer his course, even n the recesses of the most extensive forest. But if this were the fact, t would certainly prove to be one of the most incommodious compasses, hat ever was invented. For if the traveller must undergo the labour if cuting down a tree every time that he may want to know bis bearings, it is to be believed that he will soon become tired of his nstrument of observation.' Vol. I.

p.

330. Du Hamel has shewn that this fancied meridional law bas no existence id fact, but that the eccentricity of the ligneous layers n the trunk, depends upon the position of the branches, and of the leading roots, the excess being always on that side in which the most nourishment is derived. Possibly a more decisive indication of the South may be derived from the aspect of a field of ripened corn. Bonnet has remarked that when the swollen grain bows down the stem, the inclination is not accidental, but is more or less directed to the South.

One more quotation shall close our allusions to the analogies which subsists between the inventions of man, and the phenomena spontaneously exhibited by the vegetable tribe. It relates to the possibility of forming a Floral Calendar, by observing the precise season at which certain changes take place in indi vidual species of plants. This idea was suggested by Linnæus ; but we fully agree with Mr, Keith, that (however, curious-these facts may be, in a philosophical point of view) a nation inust be

a in a very low state of refinement which has not better methods of regulating the operations dependant upon the progress of the seasons. He sensibly remarks,

* Although all plants produce their leaves, flower and fruit annually, yet they do not produce them at the same period or season. ... But a great many circumstances will always concur to render the time of the unfolding of the leaves somewhat irregular.. ... Linnæus, who instituted soine observations on the subject about the year 1750, with a view chiefly to ascertain the time proper for the spwing, of Barley in ...: Sweden, regarded the leasing of the Birch tree as being the best indication for that grain, and recommended the institution of similar nim observations with respect to other sorts of grain, upon the ground of its great importance to the husbandman. But, "however plausible .. the rule thus suggested may be in appearance, and however, pleasing.

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it may be in contemplation, it is not likely that it will be ever much attended to by the husbandman'; because nature has furnished him with indications that are still more obvious, in the evidence of his own feelings, as well as perhaps more correct; as all trees of the same species do not come into leaf precisely at the same time, and as the weather may yet alter after the most promising indications..... The flowering of the plant, like the leafing, seems to depend upon the degree of temperature induced by the returning spring, as the flowers are also protruded pretty regularly at the same successive periods of the season.....

... Plants exhibit as much diversity in the warmth and length of time necessary to mature their fruit, aš in their frondescence and flowering. . Such are the primary facts on which a Calendarium Flore should be founded. They have not hitherto been very mi. nutely attended to by botanists; and perhaps their importance is not quite so much as las generally been supposed; but they are at any rate sufficiently striking to have attracted the notice even of savages. Some tribes of American Indians act upon the very principle sug. gested by Linnæus, and plant their corn when the wild Plum blooms, or when the leaves of the Oak are about as large as a squirrel's ears.. The names of some of their months are also designated from the state of vegetation. One is called the budding month, and another the flowering month ; one the Strawberry month, and another the Mulberry month; and the autumn is designated by a term signifying the fall of the leaf. So that the French revolutionists were anticipated, even by the Indians, in their new names for months and seasons. II. pp. 419_453.

(To be concluded in our next Number.)

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Art. II. An Essay on the Chemical History and Medical Treatment

of Calculous Disorders. By Alexander Marcet, M, D. F.R.S. &c. &c. pp. 181. London, 1817. THE 'HE theory of calculary concretions constitutes a subject as

well of philosophical curiosity as professional interest; and as such, may with propriety become a topic of our investigation. It is indeed right that inquiries of this nature should be made in some measure general, were it only that the circulation of knowledge among the profune and uninitiated, is calculated to keep the profession from indulging an indolent satisfaction with that kind and measure of science which has been acquired during the years of probationary studies. This feeling, althoughfar from being universal, is, we fear, by no means very uncommon; and it would probably be more prevalent and operative than it actually is, were it not that the ignorant practitioner runs the risk of having his lack of information detected by his better informed and more inquisitive patient. We would ever deprecate unprofessional interference with practical medicine, an art which can only be taught and acquired in the school of actual experience; but in the view we have just taken of the question, it is perhaps as well that the intelligent portion of the public should gain a little insight into the laws of living existence. Were it

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