The Botanic Garden Volume I Part 33

_Love out their hour and leave their lives in air._

CANTO IV. l. 456.

From the accurate experiments and observations of Spallanzani it appears that in the Spartium Junceum, rush-broom, the very minute seeds were discerned in the pod at least twenty days before the flower is in full bloom, that is twenty days before fecundation. At this time also the powder of the anthers was visible, but glued fast to their summits. The seeds however at this time, and for ten days after the blossom had fallen off, appeared to consist of a gelatinous substance. On the eleventh day after the falling of the blossom the seeds became heart- shape, with the basis attached by an appendage to the pod, and a white point at the apex; this white point was on pressure found to be a cavity including a drop of liquor.

On the 25th day the cavity which at first appeared at the apex was much enlarged and still full of liquor, it also contained a very small semi- transparent body, of a yellowish colour, gelatinous, and fixed by its two opposite ends to the sides of the cavity.

In a month the seed was much enlarged and its shape changed from a heart to a kidney, the little body contained in the cavity was increased in bulk and was less transparent, and gelatinous, but there yet appeared no organization.

On the 40th day the cavity now grown larger was quite filled with the body, which was covered with a thin membrane; after this membrane was removed the body appeared of a bright green, and was easily divided by the point of a needle into two portions, which manifestly formed the two lobes, and within these attached to the lower part the exceedingly small plantule was easily perceived.

The foregoing observations evince, 1. That the seeds exist in the ovarium many days before fecundation. 2. That they remain for some time solid, and then a cavity containing a liquid is formed in them. 3. That after fecundation a body begins to appear within the cavity fixed by two points to the sides, which in process of time proves to be two lobes containing a plantule. 4. That the ripe seed consists of two lobes adhering to a plantule, and surrounded by a thin membrane which is itself covered with a husk or cuticle. Spalanzani's Dissertations, Vol.

II. p. 253.

The a.n.a.logy between seeds and eggs has long been observed, and is confirmed by the mode of their production. The egg is known to be formed within the hen long before its impregnation; C.F. Wolf a.s.serts that the yolk of the egg is nourished by the vessels of the mother, and that it has from those its arterial and venous branches, but that after impregnation these vessels gradually become impervious and obliterated, and that new ones are produced from the fetus and dispersed into the yolk. Haller's Physiolog. Tom. VIII. p. 94. The young seed after fecundation, I suppose, is nourished in a similar manner from the gelatinous liquor, which is previously deposited for that purpose; the uterus of the plant producing or secreting it into a reservoir or amnios in which the embryon is lodged, and that the young embryon is furnished with vessels to absorb a part of it, as in the very early embryon in the animal uterus.

The sp.a.w.n of frogs and of fish is delivered from the female before its impregnation. M. Bonnet says that the male salamander darts his s.e.m.e.n into the water, where it forms a little whitish cloud which is afterwards received by the swoln a.n.u.s of the female, and she is fecundated.--He adds that marine plants approach near to these animals, as the male does not project a fine powder but a liquor which in like manner forms a little cloud in the water.--And further adds, who knows but the powder of the stamina of certain plants may not make some impression on certain germs belonging to the animal kingdom! Letter XLIII. to Spalanzani, Oevres Philos.

Spalanzani found that the seminal fluid of frogs and dogs even when diluted with much water retained its prolific quality. Whether this quality be simply a stimulus exciting the egg into animal action, which may be called a vivifying principle, or whether part of it be actually conjoined with the egg is not yet determined, though the latter seems more probable from the frequent resemblance of the fetus to the male parent. A conjunction however of both the male and female influence seems necessary for the purpose of reproduction throughout all organized nature, as well in hermaphrodite insects, microscopic animals, and polypi, and exists as well in the formation of the buds of vegetables as in the production of their seeds, which is ingeniously conceived and explained by Linneus. After having compared the flower to the larva of a b.u.t.terfly, confining of petals instead of wings, calyxes instead of wing-sheaths, with the organs of reproduction, and having shewn the use of the farina in fecundating the egg or seed, he proceeds to explain the production of the bud. The calyx of a flower, he says, is an expansion of the outer bark, the petals proceed from the inner bark or rind, the stamens from the alburnum or woody circle, and the style from the pith.

In the production and impregnation of the seed a commixture of the secretions of the stamens and style are necessary; and for the production of a bud he thinks the medulla or pith bursts its integuments and mixes with the woody part or alburnum, and these forcing their pa.s.sage through the rind and bark const.i.tute the bud or viviparous progeny of the vegetable. System of Vegetables translated from Linneus, p. 8.

It has been supposed that the embryon vegetable after fecundation, by its living activity or stimulus exerted on the vessels of the parent plant, may produce the fruit or seed-lobes, as the animal fetus produces its placenta, and as vegetable buds may be supposed to produce their umbilical vessels or roots down the bark of the tree. This in respect to the production of the fruit surrounding the seeds of trees has been a.s.similated to the gall-nuts on oak-leaves, and to the bedeguar on briars, but there is a powerful objection to this doctrine, viz. that the fruit of figs, all which are female in this country, grow nearly as large without fecundation, and therefore the embryon has in them no self-living principle.

NOTE x.x.xIX.--VEGETABLE GLANDULATION.

_Seeks, where fine pores their dulcet balm distil._

CANTO IV. l. 503.

The glands of vegetables which separate from their blood the mucilage, starch, or sugar for the placentation or support of their seeds, bulbs, and buds; or those which deposit their bitter, acrid, or narcotic juices for their defence from depredations of insects or larger animals; or those which secrete resins or wax for their protection from moisture or frosts, consist of vessels too fine for the injection or absorption of coloured fluids, and have not therefore yet been exhibited to the inspection even of our gla.s.ses, and can therefore only be known by their effects, but one of the most curious and important of all vegetable secretions, that of honey, is apparent to our naked eyes, though before the discoveries of Linneus the nectary or honey-gland had not even acquired a name.

The odoriferous essential oils of several flowers seem to have been designed for their defence against the depredations of insects, while their beautiful colours were a necessary consequence of the size of the particles of their blood, or of the tenuity of the exterior membrane of the petal. The use of the prolific dust is now well ascertained, the wax which covers the anthers prevents this dust from receiving moisture, which would make it burst prematurely and thence prevent its application to the stigma, as sometimes happens in moist years and is the cause of deficient fecundation both of our fields and orchards.

The universality of the production of honey in the vegetable world, and the very complicated apparatus which nature has constructed in many flowers, as well as the acrid or deleterious juices she has furnished those flowers with (as in the Aconite) to protect this honey from rain and from the depredations of insects, seem to imply that this fluid is of very great importance in the vegetable economy; and also that it was necessary to expose it to the open air previous to its reabsorption into the vegetable vessels.

In the animal system the lachrymal gland separates its fluid into the open air for the purpose of moistening the eye, of this fluid the part which does not exhale it absorbed by the puncta lachrymalia and carried into the nostrils; but as this is not a nutritive fluid the a.n.a.logy goes no further than its secretion into the open air and its reabsorption into the system; every other secreted fluid in the animal body is in part absorbed again into the system, even those which are esteemed excrement.i.tious, as the urine and perspirable matter, of which the latter is secreted, like the honey, into the external air. That the honey is a nutritious fluid, perhaps the most so of any vegetable production, appears from its great similarity to sugar, and from its affording sustenance to such numbers of insects, which live upon it solely during summer, and lay it up for their winter provision. These proofs of its nutritive nature evince the necessity of its reabsorption into the vegetable system for some useful purpose.

This purpose however has as yet escaped the researches of philosophical botanists. M. Pontedera believes it designed to lubricate the vegetable uterus, and compares the horn-like nectaries of some flowers to the appendicle of the caec.u.m intestinum of animals. (Antholog. p. 49.) Others have supposed that the honey, when reabsorbed, might serve the purpose of the liquor amnii, or white of the egg, as a nutriment for the young embryon or fecundated seed in its early state of existence. But as the nectary is found equally general in male flowers as in female ones; and as the young embryon or seed grows before the petals and nectary are expanded, and after they fall off; and, thirdly, as the nectary so soon falls off after the fecundation of the pistillum; these seem to be insurmountable objections to both the above-mentioned opinions.

In this state of uncertainty conjectures may be of use so far as they lead to further experiment and investigation. In many tribes of insects, as the silk-worm, and perhaps in all the moths and b.u.t.terflies, the male and female parents die as soon as the eggs are impregnated and excluded; the eggs remaining to be perfected and hatched at some future time. The same thing happens in regard to the male and female parts of flowers; the anthers and filaments, which const.i.tute the male parts of the flower, and the stigma and style, which const.i.tute the female part of the flower, fall off and die as soon as the seeds are impregnated, and along with these the petals and nectary. Now the moths and b.u.t.terflies above-mentioned, as soon as they acquire the pa.s.sion and the apparatus for the reproduction of their species, loose the power of feeding upon leaves as they did before, and become nourished by what?--by honey alone.

Hence we acquire a strong a.n.a.logy for the use of the nectary or secretion of honey in the vegetable economy, which is, that the male parts of flowers, and the female parts, as soon as they leave their fetus-state, expanding their petals, (which const.i.tute their lungs,) become sensible to the pa.s.sion, and gain the apparatus for the reproduction of their species, and are fed and nourished with honey like the insects above described; and that hence the nectary begins its office of producing honey, and dies or ceases to produce honey at the same time with the birth and death of the stamens and the pistils; which, whether existing in the same or in different flowers, are separate and distinct animated beings.

Previous to this time the anthers with their filaments, and the stigmas with their styles, are in their fetus-state sustained by their placental vessels, like the unexpanded leaf-bud; with the seeds existing in the vegetable womb yet unimpregnated, and the dust yet unripe in the cells of the anthers. After this period they expand their petals, which have been shewn above to const.i.tute the lungs of the flower; the placental vessels, which before nourished the anthers and the stigmas, coalesce or cease to nourish them; and they now acquire blood more oxygenated by the air, obtain the pa.s.sion and power of reproduction, are sensible to heat, and cold, and moisture, and to mechanic stimulus, and become in reality insects fed with honey, similar in every respect except their being attached to the tree on which they were produced.

Some experiments I have made this summer by cutting out the nectaries of several flowers of the aconites before the petals were open, or had become much coloured, some of these flowers near the summit of the plants produced no seeds, others lower down produced seeds; but they were not sufficiently guarded from the farina of the flowers in their vicinity; nor have I had opportunity to try if these seeds would vegetate.

I am acquainted with a philosopher, who contemplating this subject thinks it not impossible, that the first insects were the anthers or stigmas of flowers; which had by some means loosed themselves from their parent plant, like the male flowers of Vallisneria; and that many other insects have gradually in long process of time been formed from these; some acquiring wings, others fins, and others claws, from their ceaseless efforts to procure their food, or to secure themselves from injury. He contends, that none of these changes are more incomprehensible than the transformation of tadpoles into frogs, and caterpillars into b.u.t.terflies.

There are parts of animal bodies, which do not require oxygenated blood for the purpose of their secretions, as the liver; which for the production of bile takes its blood from the mesenteric veins, after it must have lost the whole or a great part of its oxygenation, which it had acquired in its pa.s.sage through the lungs. In like manner the pericarpium, or womb of the flower, continues to secrete its proper juices for the present nourishment of the newly animated embryon-seed; and the saccharine, acescent, or starchy matter of the fruit or seed- lobes for its future growth; in the same manner as these things went on before fecundation; that is, without any circulation of juices in the petals, or production of honey in the nectary; these having perished and fallen off with the male and female apparatus for impregnation.

It is probable that the depredations of insects on this nutritious fluid must be injurious to the products of vegetation, and would be much more so, but that the plants have either acquired means to defend their honey in part, or have learned to make more than is absolutely necessary for their own economy. In the same manner the honey-dew on trees is very injurious to them; in which disease the nutritive fluid, the vegetable- sap-juice, seems to be exsuded by a retrograde motion of the cutaneous lymphatics, as in the sweating sickness of the last century. To prevent the depredation of insects on honey a wealthy man in Italy is said to have poisoned his neighbour's bees perhaps by mixing arsnic with honey, against which there is a most flowery declamation in Quintilian. No.

XIII. As the use of the wax is to preserve the dust of the anthers from moisture, which would prematurely burst them, the bees which collect this for the construction of the combs or cells, must on this account also injure the vegetation of a country where they too much abound.

It is not easy to conjecture why it was necessary that this secretion of honey should be exposed to the open air in the nectary or honey-cup, for which purpose so great an apparatus for its defence from insects and from showers became necessary. This difficulty increases when we recollect that the sugar in the joints of gra.s.s, in the sugar-cane, and in the roots of beets, and in ripe fruits is produced without the exposure to the air. On supposition of its serving for nutriment to the anthers and stigmas it may thus acquire greater oxygenation for the purpose of producing greater powers of sensibility, according to a doctrine lately advanced by a French philosopher, who has endeavoured to shew that the oxygene, or base of vital air, is the const.i.tuent principle of our power of sensibility.

From this provision of honey for the male and female parts of flowers, and from the provision of sugar, starch, oil, and mucilage, in the fruits, seed-cotyledons, roots, and buds of plants laid up for the nutriment of the expanding fetus, not only a very numerous cla.s.s of insects, but a great part of the larger animals procure their food; and thus enjoy life and pleasure without producing pain to others, for these seeds or eggs with the nutriment laid up in them are not yet endued with sensitive life.

The secretions from various vegetable glands hardened in the air produce gums, resins, and various kinds of saccharine, saponaceous, and wax-like substances, as the gum of cherry or plumb-trees, gum tragacanth from the astragalus tragacantha, camphor from the laurus camphora, elemi from amyris elemifera, aneme from hymenoea courbaril, turpentine from pistacia terebinthus, balsam of Mecca from the buds of amyris opobalsamum, branches of which are placed in the temples of the East on account of their fragrance, the wood is called xylobalsamum, and the fruit carpobalsamum; aloe from a plant of the same name; myrrh from a plant not yet described; the remarkably elastic resin is brought into Europe princ.i.p.ally in the form of flasks, which look like black leather, and are wonderfully elastic, and not penetrable by water, rectified ether dissolves it; its flexibility is encreased by warmth and destroyed by cold; the tree which yields this juice is the jatropha elastica, it grows in Guaiana and the neighbouring tracts of America; its juice is said to resemble wax in becoming soft by heat, but that it acquires no elasticity till that property is communicated to it by a secret art, after which it is poured into moulds and well dried and can no longer be rendered fluid by heat. Mr. de la Borde physician at Cayenne has given this account. Manna is obtained at Naples from the fraxinus ornus, or manna-ash, it partly issues spontaneously, which is preferred, and partly exsudes from wounds made purposely in the month of August, many other plants yield manna more sparingly; sugar is properly made from the saccharum officinale, or sugar-cane, but is found in the roots of beet and many other plants; American wax is obtained from the myrica cerifera, candle-berry myrtle, the berries are boiled in water and a green wax separates, with luke-warm water the wax is yellow: the seed of croton sebiferum are lodged in tallow; there are many other vegetable exsudations used in the various arts of dyeing, varnishing, tanning, lacquering, and which supply the shop of the druggist with medicines and with poisons.

There is another a.n.a.logy, which would seem to a.s.sociate plants with animals, and which perhaps belongs to this Note on Glandulation, I mean the similarity of their digestive powers. In the roots of growing vegetables, as in the process of making malt, the farinaceous part of the seed is converted into sugar by the vegetable power of digestion in the same manner as the farinaceous matter of seeds are converted into sweet chyle by the animal digestion. The sap-juice which rises in the vernal months from the roots of trees through the alburnum or sap-wood, owes its sweetness I suppose to a similar digestive power of the absorbent system of the young buds. This exists in many vegetables in great abundance as in vines, sycamore, birch, and most abundantly in the palm-tree, (Isert's Voyage to Guinea,) and seems to be a similar fluid in all plants, as chyle is similar in all animals.

Hence as the digested food of vegetables consists princ.i.p.ally of sugar, and from that is produced again their mucilage, starch, and oil, and since animals are sustained by these vegetable productions, it would seem that the sugar-making process carried on in vegetable vessels was the great source of life to all organized beings. And that if our improved chemistry should ever discover the art of making sugar from fossile or aerial matter without the a.s.sistance of vegetation, food for animals would then become as plentiful as water, and mankind might live upon the earth as thick as blades of gra.s.s, with no restraint to their numbers but the want of local room.

It would seem that roots fixed in the earth, and leaves innumerable waving in the air were necessary for the decomposition of water, and the conversion of it into saccharine matter, which would have been not only c.u.mberous but totally incompatible with the locomotion of animal bodies.

For how could a man or quadruped have carried on his head or back a forest of leaves, or have had long branching lacteal or absorbent vessels terminating in the earth? Animals therefore subsist on vegetables; that is, they take the matter so far prepared, and have organs to prepare it further for the purposes of higher animation, and greater sensibility. In the same manner the apparatus of green leaves and long roots were found inconvenient for the more animated and sensitive parts of vegetable-flowers, I mean the anthers and stigmas, which are therefore separate beings, endued with the pa.s.sion and power of reproduction, with lungs of their own, and fed with honey, a food ready prepared by the long roots and green leaves of the plant, and presented to their absorbent mouths.

From this outline a philosopher may catch a glimpse of the general economy of nature; and like the mariner cast upon an unknown sh.o.r.e, who rejoiced when he saw the print of a human foot upon the sand, he may cry out with rapture, "A G.o.d DWELLS HERE."

CONTENTS

OF THE

ADDITIONAL NOTES.

NOTE I ... METEORS.

There are four strata of the atmosphere, and four kinds of meteors. 1.

Lightning is electric, exists in visible clouds, its short course, and red light. 2. Shooting stars exist in invisible vapour, without sound, white light, have no luminous trains. 3. Twilight; fire-b.a.l.l.s move thirty miles in a second, and are about sixty miles high, have luminous trains, occasioned by an electric spark pa.s.sing between the aerial and inflammable strata of the atmosphere, and mixing them and setting them on fire in its pa.s.sage; attracted by volcanic eruptions; one thousand miles through such a medium resists less than the tenth of an inch of gla.s.s. 4. Northern lights not attracted to a point but diffused; their colours; pa.s.sage of electric fire in vacuo dubious; Dr. Franklin's theory of northern lights countenanced in part by the supposition of a superior atmosphere of inflammable air; antiquity of their appearance; described in Maccabees.

NOTE II ... PRIMARY COLOURS.

The rainbow was in part understood before Sir Isaac Newton; the seven colours were discovered by him; Mr. Gallon's experiments on colours; manganese and lead produce colourless gla.s.s.

NOTE III ... COLOURED CLOUDS.