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rate threads that compose this aigrette distending as they dry, serve as levers to lift the seed from the involucre that holds it, and when out, as a parachute to prevent its coming to the ground, and to buoy it in the air.

Linnæus suspects that the ERIGERON canadense came through the air from America to Europe, not at all an impossible thing. When once that syngenesious plant has found its way into any quarter, it is sure to disperse and sow itself round the whole neighbourhood.

The funiculus (a cord which attaches the seed to its receptacle) of the dogsbane, swallowwort, periploca, &c. the calyx of several of the valerians and scabiouses form of themselves elegant aigrettes resembling those of the seed of the syngenesious plants.

Seeds are often carried by eddies of winds far from the spot on which they grew. Whirlwinds have been known to scatter over the southern coast of Spain those that had ripened on the northern coast of Africa.

Some fruits are closed hermetically and so constructed as to swim on the water. These are carried to every distance by torrents and rivers, as well as the sea itself. Cocoa-nuts, cashew muts, and the pods of the MIMOSA Scandens sometimes of the length of two yards, with many other fruits of the tropical regions, are cast upon the shores of Norway, in a state to vegetate, did the climate permit.

Regular currents transport the large double cocoa-nut of the Sechelles, to the coast of Malabar at the distance of 400 leagues from whence it was produced. Fruits brought by the sea have sometimes discovered to uncivilized nations the existence of those islands which lay to the windward of their country. By such tokens Columbus in the search of the American continent was apprised that he was not far distant from the land of which he had prognosticated the existence.

Linnæus remarks that animals co-operate with great effect in the dissemination of seed.

The squirrel and cross-bill, are both very fond of the seed of the fir; to open the scales of the cones they strike them against stones, and thus so free and disperse the seed.

Crows, rats, marmots, dormice convey away seeds to stock their hoards in out-of-the-way places. These form their winter-stores, but are often los or forgotten, while their contents come up in the spring.

Birds swallow the berries, of which they digest only the pulp, but void the stones entire and ready to germinate. It is thus that the thrush and other birds deposit the seed of misletoe on the trees where it is found; and deed destitute as this is of wings or aigrettes, it could not be disseminated in any other way, for it will not grow on the ground.

The Poke of Virginia (PHYTOLACCA decandra,) which was introduced by the monks of Corbonnieux into the neighbourhood of Bordeaux, for the sake of colouring the wine, has been since dis

seminated by the birds throughout the southern departments of France, and in the deepest valleys of the Pyrenees.

The Dutch, with the view of monopolizing the trade of nutmegs, extirpated the trees on those islands which they could not watch so narrowly as the rest; but in a short time these very islands were re-stocked with nutmeg-trees by the birds; as if nature refused to admit of such encroachment on her rights.

Granivorous quadrupeds disseminate the seed they do not digest. It is known to every one that horses infect the meadows with new weeds.

The fruit of the prickly-seeded scorpion-grass, of cleavers or goose-grass, of the wood-sanicle are all provided with small hooks by which they lay hold of the fleeces of the flock, and accompany its migrations.

There are particular plants, such as the pellitory-of-the-wall, the nettle, and the sorrell, that may be said to seek the society of man, and actually to haunt his footsteps. They spring up along the wall of the village, and even in the streets of the city, they follow the shepherd, and climb the loftiest mountain with him. When young I accompanied M. Ramond in his excursions in the Pyrenees, where that learned naturalist more than once pointed out to me these deserters from the plains below; they grew on the remains of ruined hovels, where they kept their station in defiance of the severity of the winters, and remained as memorials to attest the former presence of man and his flocks.

Distances, chains of mountains, rivers, the sea itself are but unavailing barriers to the migration of seed. Climate alone can set bounds to the dispersion of the vegetable races; that only draws the line which these cannot transgress. In process of time, it is probable that most of the plants which grow within the same parallel of latitude will be common to all the countries comprized in the entire zone of it; an event which would be one of the great blessings resulting from the industry and persevering intercourse of civilized nations. But no human power will ever force the vegetable of the tropics to endure the climate of the poles, nor vice versa. Here nature is too strong for man.

Species cannot spontaneously spread themselves from one pole to the other, the intermediate differences of temperature preventing such progress; but we may assist in transporting them, as we have done successfully in various instances. We have already transplanted the eucalypti, the metrosidera, the mimosas, the casuarina and other plants of Terra Australis into our own soil; while the gardens of Botany-bay are stocked with the fruit-trees of Europe.

The dissemination of seed completes the round of vegetation. The shrub and the tree are bared of their foliage; the herb is dried up and returns to the earth from which it came. That earth appears to us as if stripped for ever of her gay attire, yet countless germs wait but the stated season to readorn her with verdure and bloom. Such is the prodigal fertility of nature, that a sur

face of a thousand times the extent of that of our whole globe, would not suffice for the seed harvest of a single year, provided the whole was suffered to reappear; but the destruction of seed is endless, and only a small portion escapes to rise again. In no way in our view are the power of nature and the immutability of its laws more strikingly displayed, than in the successive resurrections of the types of by-gone generations.

Of the Death of Plants, from the French of the preceding Author.

PLANTS, like animals, unless destroyed by disease or casualties, are doomed to die of old age.

In many of the mucores (plants which constitute mouldiness) byssi, and mushrooms, the verge of life does not extend beyond a few days or even hours.

The herbaceous plants we call annuals die of old age considerably within the term of a year. In our climates their death takes place on the approach of winter. But we are not on that account to conclude that cold is the primary cause of the event; a milder climate would not have protracted their existence. Plants of this nature which grow under the line itself are scarcely longer lived than those which grow in the regions bordering on the poles. In both situations they perish when the propagation of the species has been secured by the ripening of the seed.

In the herbaceous plants we call biennials, only leaves make their appearance in the first year. These generally die away when winter comes; in the spring a new foliage, the forerunner of the flower-stem, is evolved. The blossom soon appears, this is followed by seed, after which the biennial dies in the same way as the annual.

In the herbaceous plants called perennials, the parts exposed to the action of the light and air perish every year after they have seeded; but the root survives in the ground, new stems are thrown up in the following spring, and blossom and seed is again produced.

In the generality of woody plants, death does not supervene until the process of fructification has been repeated for a greater or less number of years. There are trees however belonging to the monocotyledonous class, as the sago-tree (sagus farinifera,) the umbrella-tree (corypha umbraculifera)) with immense fanformed leaves of 8 or 10 yards in length, which only bear fruit once, and then die; but on the other hand, in the dicotyledonous class there are enormous trees, whose existence seems to date from before the records of history, and which, in spite of their antiquity, are loaded in each returning year with blossom and seed.

If we were to view the perennial and the woody plants as simple individuals, as such we should be naturally induced to conclude, that unless destroyed by disease or casualties they were free from the liability to death from old age; but a due conside

ration leads us to distinguish in every perennial and woody plant the new part which actually lives and grows, from the old which has ceased to grow and is dead.

I will state this in a broader way. Plants of this nature have two modes of propagating their races; one by seeds, the other by a continuous evolution of like parts.

In the first case, the seed presents us with an embryo-plant, a new and different individual, independent and unconnected with that from which it derived its existence; in the second case we are presented with a series of individuals, which issue from the surface the one of the other in an uninterrupted sequence, and in some instances continue permanently united. But whether individuals of this description are produced by seed or continuous evolution, it is certain that they escape, in neither case, the influence of time. While the succession of individuals or what we may call the race, produced in either of the ways, is on the other hand as clearly beyond the reach of age and will endure until destroyed by some extraneous cause.

We will endeavour to show how those general laws apply.

All the parts of the young herbaceous annual are susceptible of enlargement; the cells of the tubes, at first very small, are soon after extended in every way; in process of time their membra. nous walls, fortified by the absorption of nutritious juices, grow thicker, and lose by degrees their original pliancy. The mbranes once hardened, excitement ceases to be produced, and the vital functions are at an end; nourishment is no longer drawn, growth is at a stand, and the plant unable to resist the ceaseless attacks of the external agents employed by nature for its destinction, decays in a short time.

Similar causes induce similar results in the stems of the herbaceous perennials; but there the root is regenerated by a succession of continuous evolutions.

By renewals of the same nature the life of shrubs and trees proceeds. In them the liber or inner bark represents the herbaceous plant, and has like that only a short period of vegetative existence. For when vegetation revives in the woody plant on the return of spring; it is because a new liber endowed with all the properties of a young herbaceous plant, has replaced under the cortex or rind the liber of the preceding year, which has hardened and become wood.

The yews of Surrey, which are supposed to have stood from the time of Julius Cæsar, and are now 2 yards in diameter; the cedars on Mount Lebanon, 9 yards in girth, from the measurement of the learned Labillardiére; the fig tree of Malabar, according to Rumphius, usually from 16 to 17 yards round; the stupendous chestnuts on Mount Etna, one of which, Howell tells us, measured 17 yards in circumference; the ceibas of the eastern coast of Africa, of such bulk and height that a single stick is capable of being transformed into a pirogua or sailing vessel of 18 or 20 yards from stem to stern and of 3 or 4 in the waist; the baobab of Sene

gal of 10 or 12 yards in girth, and, according to the computation of Adanson, 5 or 6000 years old; all of these, giants as they are, vegetate, as does the smallest bush, solely by the thin herbaceous layer of the liber annually produced at the inner surface of their bark. The concentric layers of preceding libers constitute the mass of the wood, a lifeless skeleton, serving solely to support the new formed parts, and to conduct to them the juices by which they are fed; nor is it even necessary for these functions that this should be in an entire state. Willows and chestnuts when quite hollow at the heart, still continue to grow with vigour; but in their soundest state, strip them of their bark, and they quickly perish.

Thus reflection teaches us that the long life of the greater part of trees, and the immortality which at first sight appears to have peen imparted to others as well as to the whole of the herbaceous perennial plants, form in reality no exception to the general law which destines every organized individual to perish in determined course; since we see that the old parts of the roots of the herbaceous perennial continue constantly to die away under ground, and are succeeded by new ones, and that the concentric layers which constitute the wood or heart of the trunks of trees, are no other than the accumulated remains of by-gone generations, in which vegetation and life are entirely extinct.

This appears to us the true view of the nature of the life and death of such beings as are constantly regenerated by the successive evolutions of like continuous parts.

And we may observe that the liber which is formed on the stem of a tree of centuries old, if the tree has met with no accidental injury to affect its health, enjoys the vegetative power in as full force as the liber which is formed on that of the sapling, and that a sound well grown scion from the aged but healthy tree, affords as good a cutting for propagation as that taken from the young one, so that the race might be perpetuated by cuttings alone, without the assistance of seeds. From this we are entitled to conclude, that according to the course of nature, the progress of regeneration by continuous evolution would never be arrested, if the overgrown size of the branches and stem, the hardening of the wood, and the obstructions of the channels which permeate it, did not impede the circulation of the sap, and consequently its access to the liber.

In fine, what we call death by old age, in a tree, to speak correctly, is the extinction of that portion of a race which has been carried on by continuous evolution; the inevitable result of an incidental death in the liber occasioned by the privation of nourish

ment.

The life of trees has been commonly divided into three stages; infancy, maturity, and old age. In the first the tree increases in strength from one day to the other; in the second it maintains itself without sensible gain or loss; in the third it declines. These stages vary in every species according to soil, climate, aspect, and

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