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whose works are marked by manifold conveniences, flowing from one single contrivance, gives the acorn, and by it communicates power and glory to a nation; provided that nation has wisdom to appreciate, and virtue to co-operate with its bountiful intention. Let the branch of the oak then, with its acorns, bind the brow of America: let it encircle the American eagle, or rather let the emblem of the western empire be a CONDOR, reposing on a mighty branch of this pride and glory of our forests.

Leaving general observations, let us turn our particular attention to the physiology of the LEAF.

By FOLIATION English botanists mean the complication or folded state of leaves, while concealed within the bud; but this term expresses not that procedure of nature, by which the leaves are renewed and developed every spring, so accurately, as does the Latin word vernatio.'

In a former number we have shewn, that the bud springs from the medulla or pith of the plant;

robust. Robur nodosum was the club of Hercules, the emblem of heroick vir tuc. An oak with its acorns was held in high veneration by the renowned Romans. Pliny says, Glandiferi maximè generis omnes, quibus honos apud Romanos perpetuus. Where he speaks of chaplets, he says, that civick coronet has most dignity which is made of a branch of oak, provided it at the same time bears acorns.

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The CONDOR is peculiar to America; and is the largest bird that flies being eighteen feet from tip to tip of its wing. "The Condor possesses, in a higher degree than the eagle, all the qualities that render it formidable, not only to the feathered kind, but to beasts." Goldsmith.

Acosta, Garcilasso, Desmarchais,and Condamine, have described this preeminent bird; the last says, that he is beculiarly dreaded by the Spaniards.

Both seeds

and, by searching into the bud, we
have seen the rudiments of the
leaves; and when we penetrated
still deeper, we discovered, that the
tud, like the seed, contained the
but
epitome of the future plant ;
during winter it wants the power
of unfolding its parts.
contain the primordia
and buds
plantarum : buds therefore differ
from seeds only, as the living fœtus
differs from the egg of an animal;
so that buds are seeds in a more
advanced stage of vegetation. We
have already remarked, that some
buds contain flowers, some leaves,
and some both; and that an ac-
curate discrimination of them was
of importance in the process of
budding. To watch the vernation
of the embryo bud, the gradual
unfolding of the fetal leaves and
infantile flower, is a pleasing spe-
culation; for the leaves are com-
pletely formed, and fairly rolled
up for evolution, many months be-
fore they begin to expand the
study of the anatomical structure
of the full expanded leaf and its
functions, is equally delightful.-
We shall pass silently over the
nomenclature of leaves, which is
apt to discourage young botanists
unused to geometrical writers in
the Latin tongue, and shall pursue
the more pleasant task of exhibit-
ing, as far as we are able, the struc
ture and the functions of the leaf.

When we are told, that a leaf is a part of a plant, extended into length and breadth, in such a man

*There is not only the Folium bifdum, trifidum, quadrifidum, quinquefidum, and bipartum, tripartum, quadripartum, and quinquepartum, but there is the folium compositum, decompositum, and supradecompositum; and the folium amplexicaule, and semiamplexicaule, and an hundred others, having reference to the shape of the leaf merely. Good sense has hardly fair play when thus oppressed with hard words.

ner, as to have one side distinguishable from the other,'* the naturalist receives but little information; and we obtain but little more, when we are told, that they are the organs of motion;'t but, when we say, that the leaves are the lungs of a plant, we convey an idea more consonant to truth and nature for we find that a leaf will die, if its upper or varnished surface is anointed with any glutinous matter; or when placed in an exhausted receiver. If we should say, that the leaf combines the office of lacteals and lungs, we shall come still nearer truth. While our stomachs digest solid food, our lungs digest air; so that what is performed by two organs in animals, is performed by one in plants; let us then examine this organ and its functions.

The LEAF is attached to the branch of the plant by a short footstalk. From these foot-stalks a number of fibres issue, which, ramifying in every direction, communicate with each other in every part of the leaf, and thereby form a curious network. The intermediate substance is greenish ; and may be eaten by insects, or destroyed by putrefaction, while the fibrous part remains entire, constituting the skeleton of the leaf. There are, however, two layers of fibres in every leaf, forming two distinct skeletons; the one belonging to the upper part of the leaf, the other appertaining to the lower. It is very difficult to demonstrate the anatomy of a leaf; but we have reason to conclude, that the seven essential parts of a plant, enumerated in the fourth number, are extended, rooled out, and extenuated throughout the leaf; so

* Miller. + Linnæus. Landskips, painted by the best masters, are not green.

that if you slit a leaf with scissors, you cut through as many different parts of the plant, as if you cut through the trunk of a tree. The whole leaf is covered with a portion of the epidermis, or that scarfskin, which covers the stem and stalk of the plant. Between this thin membrane and the cortical net-work, are placed the absorbent vessels, together with what we presume to be the absorbent-glands. Dr. Darwin assures us, that there is an artery and a vein in a leaf; and that the artery carries the sap to the extreme surface of the upper side of the leaf, and there exposes it, under a thin moist membrane, to the action of the atmospherick air; then the veins collect and return this circulating fluid to the foot-stalk, just as the artery and vein operate in our lungs. It is hardly fair to compare the leaves of a plant with the respiratory organs of the more perfect animals; but rather to the breathing appar. atus of insects, or, what is perhaps more to our purpose, to the gills of fish.

When the structure of any organised body is too subtle to come within the scrutiny of the human senses, we must have recourse to analogy, and from the truths we discover, and the observations we make, we must judge of the oper ations in similar bodies; for we can form our opinion of that, we know not, only by placing it in comparison with something similar to that we know. The structure of certain large-leaved plants, that grow in water, are remarkably conspicuous; and the gills of fish resemble, in structure and office, the leaves of these aquatick plants. Duveney and Monro have scrutinized the gills of fish; the former found, that those of the carp contained four thousand three hundred and

́eighty-six bones, which were moved by sixty-nine muscles: and the latter informs us, that, in the gills of the skate fish, there exists one hundred and forty-four thousand folds or subdivisions. This manifold structure gives this respiratory organ a surprising extent of surface. These subdivisions terminating in innumerable points, resemble fringe; but, when examined by the microscope, appear like down; yet is every part crowded with blood-vessels, being ramifications of the pulmonary artery and vein. The whole extent of the gills is covered with an exceedingly fine membrane, in which the microscope discovers a still finer network of vessels. By such a structure the fish exposes a greater surface of blood to the water, than is exposed to the air, by the internal membrane of the air-cells of the lungs of quadrupeds; and that for the same purpose, namely, imbibing uncombined oxygen, which is the material or pabulum vitæ, equally necessary to fish as to land animals. Now, if we compare the structure of the gills of fish with that of the leaf of aquatick plants, we can discern a great similarity; but the limits of this essay do not allow us to run the parallel so far as we might.

As a tree cannot go in search of food, like an animal, it is forced to draw its nourishment from within the narrow sphere of its existence; it therefore extends its roots through the surrounding earth, by which it draws in sustentation, as through so many syphons. These imbibing vessels of the roots may be compared to the lacteals in animals. This chyle, or sap, ascends to the leaves, and is there changed into a more perfect fluid, answering to the blood of animals; it is still further exalted in the flower,

in order to perfect the seed, and continue its kind. The roots are sufficient to supply nourishment to a large tree during winter, when divested of its leaves, and when the vegetative life reposes in winter quarters* but, stimulated by the warmth of spring, the vegetable ens awakes, and, when the process of vernation has fairly begun, then the tree has more to do than merely to support its own existence; and therefore it spreads through the air its numberless leaves, which are nearly equivalent to the stomach and lungs of animals.

That the sap ascends to the leaves is proved by the bleeding of vines early in the spring, before the leaves are formed, there being no leaves to receive it; but, when these elaborating organs are formed, the vine ceases to bleed, because the sap flows into them for rectification ;t for, while a vegetable is growing, it is continually going through a regular series of changes, losing the properties of one substance and assuming those of another; thus mucilage in a young plant becomes starch in the old; what in green fruit is acid, in a ripe fruit is sugar.

But the function of the leaf is not perpetually uniform, as in the lungs of the more perfect animals; its operations differ in the day, and in the night. In the day the leaves of plants exhale moisture and oxygen gas, and absorb carbonic acid gas; but during the night they emit carbonic acid gas, and absorb oxygen gas. In plainer terms, they exhale, in the light of the sun, salutary or vital air, but in the dark they emit deleterious air : one of

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these operations is performed by the varnished* side of the leaf, and the other from the rough or under side.

As air and heat are necessary to the life of a plant, so is light to its health. The want of light prevents a plant's forming its proper juices, deprives it of its green colour, and prevents the impregnation of its seed. It is the smooth side of the leaf which is acted upon by light, and is that part, by which a plant, in a great measure, lives; hence the leaves of many delicate plants shut up, so as to cover this smooth side on exposure to noxious vapour, or darkness, or to screen it from an extremely fierce sunshine. In order to make a distinction between the sensation of heat and the cause of it, the word caloric has been adopted; it is a body, and so is light. The sun is

* The varnish of the leaf is found to be bees-wax.

It is remarkable, that the leaves cannot prosper without light, yet seeds germinate best in the dark.

LIGHT is an elastick fluid, that is reflected from certain bodies which it cannot penetrate it is also possessed of chemical affinities, by which it enters into combination with other substances; sometimes occasioning their decomposition, and sometimes it is extricated from its combinations. It gives to vegetables their colour, and contributes to their smell, taste, and balsamick principle. It enables the leaves of vegetables to emit streams of oxygen gas, or pure vital air.

OXYGEN, or the acidifying principle, is found only in its combinations. The oxygen gas is the result of the combination of oxygen with caloric. It exists in atmospherick air, in the proportion of 27 to 100, and is heavier than the air of the atmosphere. It is absolutely necessary to respiration, hence termed VITAL AIR. During the action of breathing it enters our blood by the vessels of the lungs, giving to it a vermillion, colour, and an augmentation of its vital powers.

the source of both; for he emits two kinds of rays, one calorific, the other colourific; the first occasions heat, the other colour,

With what different eyes does the philosopher and the uninformed husbandman view a tree, waving in the full glory of its luxuriant foliage! Ask the woodsman for what a tree was made-he will tell you to bear nuts; to be cut into boards; to burn, to keep him warm, and to cook his victuals. Ask the naturalist, and he will tell you, that they are an important, nay indispensible link in the chain of human existence; insomuch, that were the Parent and Legislator of nature to cause every vegetable on earth to be at once annihilated, the atmospherical air would directly become a putrid mass of every thing that is noxious, and man, and every other terrestrial animal of similar construction, would soon turn into a mortified lump of corruption. The leaves of all sorts of vegetables are in fact so many laboratories for purifying the air we breathe.

During winter, when the surface of the earth is bound up with frost, with snow, little or no putrefaction encrusted with ice, and covered takes place; then the vegetable kingdom appears as if dead; the trees, divested of leaves, seem like the sun begins to diffuse its warmth so many dead sticks; but when over the earth, promoting that general tendency to corruption, to which all dead bodies are liable, then the trees soon exhibit a wonderful scenery, and the leafless branches,by displaying, all at once, their foliage, increase their surfaces many thousand times. The leaves are so arranged on the branches, as to expose their varnished surface to the direct influence of the sun ; and, if forced out of that po

sition, they will turn themselves; for leaves are more greedy for the light of the sun, than for the influence of its heat.*

It is from the under, or rough side of the leaf that the azotic or unwholesome air is emitted, while the oxygen, or pure vital air emanates from the upper or smooth surface; but not before the sun has shone some time upon it. This distillation of pure vital air by the leaf diminishes towards the close of day, and ceases altogether after sunset, when unwholesome air is emitted by the rough side of the leaf; and the next day, soon after the rising of the sun, the smooth or upper side recommences its function. Hence we learn, that it is unhealthy to tarry in the deep shade of trees during the night. 'Surgamus,' says the shepherd in Virgil, solet esse gravis cantantibus umbra.'-Let us rise; for the evening shade is unhealthy to sing ers; and, he adds, even the juniper is now noxious. Ill-scented and even poisonous plants equally afford salubrious air in sunshine. It is remarkable, however, that, while leaves perform this salutary process, flowers render the surrounding air noxious, even in the day time. Gathered fruit has, at all times, a deleterious quality. A peach, in a few hours, rendered a body of air, six times its own bulk, so entirely poisonous, that an animal could not breathe, nor a candle burn in it. A rose kept in a glass, so much infected the air, as to render it unfit for respiration.t Persons have been found dead in their beds, whose lodging rooms have been crowded with flowers: others have been suddenly affected with dizziness, nausea, and head

* See Ingen-houz passim. + See Priestley on air.

ache, on going into a green-house of flowers, that had been shut up closely during the night. While a growing vegetable is capable of this two-fold operation, it absorbs whatever putrescent particles it finds in the surrounding earth and air. A sprig of mint, put into a jar of air, rendered foul by animal putrescency, will revive, and grow surprisingly; and will moreover correct that air, so that an animal shall be able to breathe in it.

Here is the proper place to remark, that the ocean, when agitat. ed by winds, yields oxygenous gas; and that azotic, mephetic, or noxious air is corrected by being strongly shaken with water. Hence we learn that the two grand correctors of the air we breathe, are, first, the agitated ocean, and secondly, living vegetables, while operated upon by the rays of the sun.

If we reflect upon what has been said, it will appear, that plants have their private virtues, and their publick ones. Beside the peculiar medicinal and nutritive qualities, which some possess, the great family of plants, or what is called the vegetable kingdom, conspire to form one grand apparatus for purifying the atmosphere, and rendering it fit for respiration; and these may be called their publick virtues. In this view no vegetable grows in vain, whether in the interiour of this vast continent, or in the wilds of Africa; for the leaves of all, whether ill-scented, acrid, or poisonous, elaborate the air they contain, and pour down a shower of depurated oxygenous or vital air, which, diffusing itself through the common mass of the atmos

SIngen-houz placed twenty-four French beans in a quart jar, which rendered the air, in one night, so poisonous, that a chicken, put into it, died in about twenty seconds.

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