Imagens das páginas

ttide of human curiosity they sought iu cultivation the solution- of this problem. In vain did J experience, disprove this system. They went be- I yond our record and it membrance, and bid in the obscurity of antiquity the ignorance of an j origin which they were forced to admit must be i sought after the creation. _ This theory, nevertheless, could not be sufficiently satisfactory to explain the origin of some new races which they had seen appear in gardens tmder the eyes of their contemporaries.

The graft and the slip (cutting) then came to the assistance of cultivators. They commenced I by believing that the subject or stock grafted can sometimes influence the grafted bud in modifying its juices, and they Imagined the existence of extraordinary gratts which', uniting very different species, seemed destined to produce new races having the characteristics of both.

Others attributed these marvellous fruits to some capricious combinations lbrmed by the union of two buds. Others finally established, in substance, that by the single fact of the graft being repeated several times on the same mdividuals an improvement in the plant was obtained.

There have been agriculturists who thought themselves able to change or modify the taste of vegetable productions either by infusing the seed in substances sugared or aromatie, or by the introduction of these substances into the pith of the plant; and the ill-success of these operations was always attributed to a defect in the manner of proceeding rather than to an insufficiency f)f the means employed.

It is to these different methods that have been attributed all the phenomena of the vegetable system, of which the cause was not understood.

Thus it has been believed, and is still believed perhaps, that the absence of spines and down belonging to certain vegetables is only the effect of the change of climate, of long cultivation, or of the graft.

In like manner, to the multiplication by slip or by layer, the loss of the pistils of certain plants, and the sterility of certain fruits have been attributed, in which fruits it was believed that th's method of multiplication acts to obliterate tho female parts and to increase the volume of the fruit. The lack of proofs was hidden in the necessity of following those methods during a succession of several generations, and the system was supported by the example of several sterile plants, such as the Persian lily, the snowball, the syringa, and many other ornamental bushes; and on that of the barberry bush, the medlar tree, without seeds, &c. This theory could not, it is true, be extended to annual or biennial plants which the seed pnduce every year, and in which we so often see examples of sterile flowers. But they found in their principlesn very plansible explanation of sterility,-and they attributed the double and semi-double flowers to tho force of cultivation, imagining that this agent, aided by surrounding substances, occasioned the translormation of the fructifying parts into petals.

Finally, wishing to give an explanation of those monstrosities which the vegetable world constantly presents, they regarded them as diseases produced by exterior causes which they have

never determined, and they attributed to these unknown causes the variegated coloring of flowers and the diversified foliage of trees, together with the extraordinary forms of those fruits which offer excrescences in the pericarp, or other similar phenomena. All these opinions have reigned for centuries among agriculturists, and it is but recently that they have begun to forsake them. It is certainly interesting to discuss them, and important to establish or refute them. This is the task which I have undertaken. I have employed my leisure in examining them with the principles ol a severe philosophy, and submit them to the analysis of observation and experience. The first fact which it was necessary to examine was to know if wild trees existed which the graft or culture has changed into fine varieties. This question holds the solution of a problem of vegetable physiology which appears not to have hitherto occupied the learned, viz.: What is the influence of these agents (the graft and cultivation) on vegetables?

Art. III.—Influmve of the graft upon vegetahtes.

It must certainly he acknowledged that the graft as well as the culture and soil may influence tho development of vegetable organs. "A grafted tree is an individual forced to live upon a stock not its own, but from which it must draw its nourishment, so that only the subject of the graft can be assimilated to the soil. If its organs are adapted to furnish the graft all the aliment of which it can make use, then the graft will take on an extraordinary growth, which it would not have equalled on a less thrifty stock. If the stock which bears it be unable by its organization to supply the food it needs, then will it remain meagre and spindling.

These different circumstances, as well as the culture, may produce the phenomena presented by the wild service tree (Sorbvn Aucuparia), which, grafted upon the hawthorne, (Mespyhts Oxyacontha) grows, it is said, with more than usual rapidity, and attains more than its wonted height and fruitfulness. Also that of the wild apple, which, grafted upon the paradise apple, becomes a slender shrub whose branches grow hardly ten feet high.

These phenomena are due only to the abundance or lack of nourishment, and ('resent no other effect than a greater or less development of the different parts of the plant. Wo remark one thing still more striking in ordinary5 grafts. Every grafted plant appears to display, at least for a time, a luxuriance of foliage more marked than the seedling, for instance, if the graft has been nut into an individual of this nature; but i his is due to a very simple cause. The seedling develops many branches. It gives fruit generally once in two or three years, and when it does bear, t ho tree is so loaded down that it can only nourish them all with difficulty. Prom the time it is grafted several changes are effected. Its plump and busby top disappears and is replaced by a single branch, which has for its own nourishment all the sap which supported that large quantity \ f foliage. To be sore the graft may enlarge afterwards, but it never replaces the quantity of branches whicu crowned the original tree. ' A grafted tree i? always less large and busby, and hence the foliage is better nourished «md more beantiful, and its fruits, which arc less abundant, arc of grenter size and more agreeable llavor.

Another circumstance also influences, perhaps, the greater elaboration of fruit in the grafted tree. •

The graft unites a branch of one variety to a stock of another variety. This union, which is not natural, forms always a kind of knot at the point of insertion, which may check the rapidity of the flow of sap; and we know that on account of this slowness m the current of the sap, buds fed by it produce fruit rather than branches.

A tree which bears but little may be rendered fruitful by rubbing off the bark at its foot. The cultivators of vineyards bend the vines or break them a little at the place where they wish the fructification to commence; and I have several times obtained oranges of extraordinary size by twisting the branch which bore them.

All these means have been long known to cultivators, and it is no longer doubtful that this effect is due only to the great slowness in the flow of the sap, which thus influences the quantity and quality of the fruit.

But such are the limits which nature has fixed lo the influence of the graft upon vegetables. It facilitates or improves their development, but never changes or modifies their forms, juices, or colors. Never has the wild pear been transformed by the graft into the butter pear, nor the butter pear into the muscat pear; never has the bitter orange been so improved as to lose its bitterness by grafting. I have a stock of this species which I have grafted three times upou itself, graft upon graft, but it gives mc only larger fruit, differing in no other way from that of the plant which furnished the bud.

The graft is nothing more than a kind of slip. It transfers the bud of one plant to the stem or body of another; and this bud, which encloses within itself the rudiments of the vegetables destined to grow from it, draws from the stock on which it is placed the juices necessary for its nourishment in the same manner as the slip draws them directly frdm the earth. It is possible that, from the passage which these j uices are forced to make through the roots and trunk of the plant, they reach the fibres of the bud more elaborated than if drawn more directly from the soil; but whatever may be their condition when they enter the bud, they are there always modified by its organs as arc those elements drawn from the air, and as those taken from the earth would be, if it were placed with its own roots directly in the soil.

Experience has confirmed these principles, and it is now established that the graft is useful only in perpetuating species or vaneties without improving them. I have made constant observations on this subject during more than fifteen years, by keeping beside tho grafted plant the plant which furmshed tho bud. I have grafted oranges upon lemons and lemons upon oranges. I have grafted sweet oranges upon bitter oranges and bitter oranges upon sweet ones; apricots on prunes and peaches upon apricots; and I never could recognize the least difference between the fruits given by the plant which furnished the graft and those of the plant which received it. I never obtained from these operations any other

result than that of preserving rare varieties, which could not be propagated by seed, for the double reason that they but rarely contained any, and that when they did, we could obtain from them usually only degenerated varieties.

The theoretic principles which prove the insufficiency of the stock and of the sap to effect changes in the product of the graft, can not be equally applied to those remarkable grafts formed by the union of two or three buds, the manner of which occurrence is described in the works of ancient writers upon agriculture, and to which it is still pretended mixed species are due, such as the orange <U bizarrerie, which partakes of the character of the orange, the lemon, and thecitron.

Wff have great difficulty in conceiving ho w two half buds, applied the one upon the other, can amalgamate and form one single bud partaking of the nature of the two. I would not dare cite my experience to prove that two different buds united together inserted upon an analogous stock, or even placed in the earth, perish if too much mutilated, or develop, each one separately, its scion.

The ill success of these operations would be only a negative proof, which could not destroy the facts if any existed; but I challenge the gardeners to cite me an example, supported by impartial observations, whose exactness they can guarantee. Moreover, if in presenting me such an example they offer me only such individuals as those I possess, and such as I have seen in Liguria, in Tuscany, and such as are known in France under the name of orange de bkarrerie, I would venture to-contradict them respecting it.

The anatomy of the tissue of these individuals would furnish me an irresistible argument. This tissue does not present traces of three buds to whose unions the hybrid is pretended to be due. It shows only a branch which bears at one time, but isolated under distinct leaves, buds of three species and buds which give mjxed fruit, without, however, enabling us to recognize in these species of embryos anything announcing this mixture.

I will not speak of those imaginary grafts by. which some have pretended to make branches of the fig, grape, rose, And jasmine grow on orange and lemon stocks. I have several times seen such phenomena in Tuscany and Milan, and confess to have been deceived by them; but having been a long time cheated by those gardeners, who sold at exorbitant prices ridiculous recipes for obtaining these extraordinary unions, and after having lost, by making trial of them, several orange stocks, I finally succeeded in discovering the fraud, and am convinced that these heterogenous unions do not exist in nature. I bought a vase containing an orange stock on which a fig scion seemed to be grafted. As soou as 1 got possession of it I opened the stock' where the fig branch was inserted, and discovered that this stock was hollowed out inside, and that through this hole in the interior the would-be graft found its way to the soil, thus living upon its own root instead of that of the orange tree. This discovery completed my conviction that a difference really exists in the organs of different vegetables as well as in the organs of animals, nnd that from this difference of organization the difference of products results. I know that in

the vegetable kingdom details escape the observation" of the physiologist, and it is extremely difficult to give some of the comparative anato'mica) appearances of vegetables, but it is for this reason no less true that differences may exist and be as unchangeable as fn the animal kingdom. Every species has its determined forms, which may bo destroyed but not modified, and whatever the nature of the stock which nourishes the plant, il will always give the product proper to its species. t

Art. IV.—Influenee of culture and soil on plants.

Culture and climate have appeared to many writers more powerful than the graft, and they . have attributed to them the very decided changes "in the secondary characteristics of trees. It is principally to the force of culture that they attribute the sensible difference existing between the wild and cultivated trees. But it is easy to see that this is a mistake in their judgment, aud that they attribute these differences to culture or the graft, merely because these are the processes which always accompany the individuals—which undergo a change and become improved fruit, and becanse these are the means of multiplying the number of the improved individuals. Whereas these arc mere accidents; they have, becanse constantly used, been considered the causes of the changes in the fruit.

Nature gives some trees which bear ordinary fruit and others which bear fine fruit. The first, always being grafted when in our gardens, bears its own peculiar wild fruit only when found in the woods; and the cultivator who sees them there in a degraded condition concludes that this degeneration is due to the want of cultivation. The trees bearing fine fruit, being seen only In a state of cultivation, and multiplied by the graft only, the cultivator, ignorant of the origin of their ancestors, judges that they owe their improvement to the graft and the culture which they have undergone. I say the cultivator judges in this manner on account of this ignorance of the first original treo which gave these different results which he observes; becanse there has never existed a writer, to my knowledge, who has carefully noted how ono of these changes has occurred. They all speak of the changes and noto the difference which exists between those individuals found in the woods and those found in the gardens, but no one bas seen this change take place on one and the same in dividual. I say all see it through the dimness of ages, and their conclusion is the result of con jecture rather than of observation.

But a close and continuous attention to nature will show that these differences, which exist in two distinct individuals, as, for instance, the pear of the forest and the pear of cultivation, never appear successively on the same individual. I call an individual the plant which exists on its own stock, and which enjoys the life given it by Nature, and I also term an individual the collection of all the plants which proceed from a single germ, and consequently form only one single plant, which may be multiplied without changing its character, either by passing successively on to an infinite number of stocks as a graft, or by forming by means of slips an infinite number of stocks

wn, having a root in the earth, and pro: in this manner its own life, as well as

of its owi longing i

that of the species, and thus varying infinitely the places and modes-of its existence, but always bearing in itself the principles of organization received in its conception.

The individual which perished on the root where it germinated, and that which renews for the in ill inn Ut time, it may be, its life, in a graf t or a slip, have a siugle and common origm, and hence arc one and the same individual. 'This individual, though infinitely multiplied, will always bear in the numberless subdivisions of its being the same characteristics and the same aspect which it had in the beginning. To illustrate, take the sugar-cane. In India, beyond the Ganges, there are several varieties of this plant which arc propagated by seeds, but in-San Domingo, where it is reproduced by slips, only one variety is known. It has been cultivated there since 1600, with different methods and a variety of soils, and still remains unchanged. Neither the processes of cultivation nor the difference in soils have improved it in the course of two centuries, and the only reason why it has not degenerated is because it has always been multiplied by cuttings.

This fact is perfectly in harmony with the theory of the manner "in which culture affects vegetables. Nutrition is the most powerful means by which they can be influenced in cultivation. The nourishing juices, of which the earth is the principal vehicle, arc everywhere of the same nature; chemistry has proved that the samo elements unite to form, the acorn in the oak tree^ and the orange in the orange tree. It is in the* different organs of the diverse genera of vegetables that these same principles are decomposed, elaborated, and finally acquire forms and properties widely different from each other.

Now, can we suppose, without wounding the principles of sound philosophy, that this passive material, which is designed only to receive modifications from the different agents by which it is elaborated and used—that this can react upon those organs or agents and change their existence, a work so marvellous t hat >, ature only can perform it? •'

It has been held that the multiplicity of petals, which form double flowers, and the certain lustiness of some varieties arc due to a superabundance of nutrition. But this formation of petals is not the simple development of a principle pre-existing in the flower. It is a real change of the male and female parts into corollas; aud the lux-' uriance of these beautiful varieties bears in the leaf and in the fruits new forms, which distinguish them from others and constitute them distinct races.

Nature has fixed for all races a maximum and a minimum of development which no cause can surpass. When a plant has little nutriment it becomes feeble and languishes, but it will die before departing from the characteristics of its species. If well nourished it attains tho maximum of its growth, but if engorged it refuses the superabundance, or, if forced to absorb, it is injured; its canals are blocked up, its organs affected, its vital functions changed, and it perishes. The facts we possess are in harmony with these principles. Wc find double flowers only in species which are multiplied by seed. Those propagated by slips or the grail uever present this phenomenon. We never flud it in the jasmine, the hortensia, nor in any of those exotics which in our climate yield, no seed. But they are certainly cultivated with as much care as roses, hyacinths, or carnations; but they never present the caprices of these beautiful varieties, which reappear every day in our gardens under new forms and with a mixture of the most charming colors. The error of these cultivators has been still more extraordinary in regard to sterility of plants, which they have attributed to the mode of propagation by slips or by layers. All these opinions could result only from erroneous reasoning.

Wo have already seen that—having observed that plots of ground were covered with choice varieties while the woods were full only of wildroncs —it was inforrcd that it was culture which had changed the savage varieties to fine ones, so that these last arc now called domesticated varieties. In this case of tho sterile plants—having observed that they were multiplied only by the slip and the layer, it has been inferred that it was the mode of propagation which effected in the plant subjected to this operation for several generations, the insensibly gradual loss of its stamens and pistils, and finally produced sterility. Ilere it is easy to see the effect has been taken lor the cause. These plants have been considered sterile because propagated by the cuttings, whereas the contrary is true, and they arc propagated by the cuttings becansc thuy are themselves sterile; otherwise" it would follow that all plants multiplied by the slip would be ntcrile, which is not the case. Examples might be given in abundance of plsnts bearing fertile seeds, which have long been multiplied by the cuttings, as the olive ana the grape; and a great number of superior varieties are produced by the slip only to keep them from degenerating.

But the most conclusive proof of the futility of this belief is the fact that these plants of sterile flowers all have their type, which is not sterile, and whose seeds have probably given the sterile variety which has been multiplied by cuttings. Indeed, wc sometimes fmd this variety in the woods, where nature certainly has used no grafting knife, as, for instance. In the sterile snowball (viburnum opulus sterilis) beside the ritmrnnm opulus or snowball of fruitful flower.

I shall not occupy my time in discussion upoo tho influence of infusions of sugary substances and other similar processes by which all the ancient writers pretend to change the taste and color of fruits; all these notions are now relegated to the books on agriculture of the seventeenth century, and there is no cultivator, however little enlightened, who ii not convinced of their uselessncss.

Besides, these errors cannot but disappear from the moment that wc aro convinced that nutrition (by which means the cultivation of the soil acts upon plants or trees,) influences only their simple developments, but that forms, colors, properties, can only be changed by the seed.

Such is the march of nature in all the chain of organized beings. Generations vary iufinitely, but individuals never change. The negro and the white man trive rre to numerous mulattoes,

but the negro transported to the eternal snows of the North will suffer no change any more than will the while man under the burning sun of Africa. The giant will procure his stature amid the most cruel want, and the dwarf will never change his proportions, though supplied with the most nourishing food. Nature has determined the forms of all beings; she has fixed the principles of their organization in the embryo, and nothing can alter them. They resist every force that surrounds them, and ever preserve, amid the contiuual variation of nourishment and soil, the original impress received from the hand of Nature.

Aiit. V.— The reproduction of plants bj fltr seed.

The seed is the only source of variotios in vegetables. It is only by this means that nature effects those wonderful transformations cvory day witnessed, but too little understood. The majority of cultivators acknowledge this fact; and even those who attribute beautiful varieties to culture also agree that many aro furnishod by the seed.

We propose, by the following experiments recorded bv a French naturalist of great experience, to show the results of reproduction by seed.

Experiment I.—I sowed, during several years, seeds of tho china orange (citrus civrantium sive7tse), of a fine shining skin. I always obtained sweet orange trees, of which a part bore oranges of a thick, rough skin, and a part beautiful fruit of a skin still finer than the original which furnished the seed. The same thing occurred in the sowing of ordinary oranges of thick and rough skin—there grew up several trees of beaut i ml fruit, and one stock, whose leaves were like shells in shape, but the fruit very ordinary and seeds few, and even those very poor.

I made the same experiment with the peach tree; seeds from peaches borne on the same tree gave several varieties, for the most part of ordinary fruit, but a few finer than the original planted; but the stones never gave a cling-stone peach, nor a cling-stone the ordinary fruit.

The almond gave the same result. Sweet almonds produced only sweet almond trees. There was some difference in the hardness of the shell, but I never obtained a single bitter almond.

Experiment II.—I sowed seeds of the red orange (citrus aurantivm tinense, hicrochunticum, fructu sanguineo). The trees which came from these produced only ordinary fruit of orange color.

Experiment III.—I sowed lemon seeds taken 'from lruit gathered in a garden where lemon and citron trees grew together, and obtained many trees, whose fruit presented a series of varieties, from the lemon to the poncire, but the larger part of them were simple lemons. Tl<ose having the characteristics of the poncire produced no seeds.

Experiment IV.—During a long series of years I sowed seeds of the sweet orange, sometimes taken from seedlings, sometimes from seedlings grafted on a sour orange stock or a lemon stock, but always obtained sweet oranges. This result is confirmed by all the gardeners of Finale (a small town in tho north of Italy) for moro than sixty years. There is no example of n sour orange produced from a sweet seed, nor of a sweet orange produced from a sour seed.

From these experiments are obtained the following cooduBioas:

Consequenee /.—The seed perpetuates the species and is the source of varieties. It produces more- frequently varieties inferior to the mother plant; sometimes, however, those superior to it. It never departs from the species unless the fecundation of another species gives it the germ of a hybrid. (Exp. I and III.) This occurs equally in the seed of the seedling and that of the grafted tree. The trees which come from them reproduce the same species which gave the seed, aside from the modification of varieties noticed above. (Exp. IV.)

Consequenee 11.—The seeds of monsters, when they aro found, produce only ordinary fruit, which indicates that this extraordinary fruit is only u variety, and that the variety returns to the type in the seed. (Exp. II.)

Consequenee III.—The seeds of the a weet orange produce only sweet orange trees; sour orange seeds produce only sour orange trees. These two orange trees arc preserved and perpetuated by the seed, and are, thorefore, distinct species. The ordinary peach never produces the clingstone, nor the cling-stonc the ordinary peach, and hence they are two distinct species, and can not degenerate from the ono to the other. The same is true of the swoct and bitter almond. (Exp. I and IV.)

Consequenee IV.—The seeds of lemons growing in a garden where lemon and citron trees grew together, produced poncircs. This fruit is, therefore, probably a hybrid of the citron, the absence of seeds showing that it is due to a foreign fecundation. (Exp. III.)

Akt. VI.—The theory vf trydMc reproduction.

My experiences as a whole sufficiently substantiated the most of the phenomena presented by the multiplication from seed. They determined the origin of varieties in plants. But it remained still to know the secret canses of these results—why nature departed in some cases from the system generally followed in reproduction.

Every seed in nature is only the germ which is to renew the individual which produced it; but some vegetables we have seen depart from this system.

What is the cause of these exceptions? I observed that these phenomena took place from preference in the seeds taken from plantations where there was a mixture of species or varieties; that lemons gathered in the garden where there were citrons gave more varieties than those from trees standing alone; that the seed of the black cabbage which hod flowered in the midst of many cabbages of different varieties, produced frequently cabbage remarkably well headed, much sought for its delicacy and whiteness; thut the seed of the crowfoot of several colors, which I cultivated in quantity in plots of my garden, gave very often double flowers, while this did not happen with the seeds of the same flowers which I had cultivated in vases, each by itself, before the establishment of my flower garden.

All these observations presented a certain analogy between the hybrids and the monsters, and I suspected that the influence of the pollen which effected the mixture in hybrids might also enmo

sterility, and those modifications ut leal kuown as curled or streaked.

A crowd of reflections were presented to my mind. It is recognized, I reasoned, that two different principles must co-operate for the reproduction of all organized beings. "Wo know that when theso principles belong to different specie., monstrosities result, such as mules among animals, and among vegetables tho mixed plants known under tho name of hybrids.

Why may not this principle, which effects so many phenomena, be the cause of moustcrs and varieties? These, it is true, do not prove the mixture, for they arc produced even from the seed of isolated trees; but is it necessary^that tho principles of two different species unite in fecundation in order to change the physiognomy of the product f Cannot this be as well accomplished by different properties of the two agcuts in the eame species, and perhaps also by a difference in the force of their action, or by a defect iu the analogy in their principles? Is it not from the different proportion of these two agents of organic reproduction, that results this marvelous variety, distinguishing all animals by a peculiar physiognomy? There is no fruit in the same plant "even which is exactly like any other. Might not the inequality which exists amoug

I the fruits of a single tree, as we observe it among

i the children of the same father, exist still more pronounced between the fruits of two different plants, although of the same species? Should not the pollen of the flower of one peach tree have a family likeness which would make it different

I from that of the flower of another peach tree, and if these two peach trees, modified in their conception by fecundation, were already marked by those differences which constitute varieties, would not the reunion of their flowers produce a new combinatiou which would constitute a variety still more irregular? Finally, what might not the difference in the proportions and the mixture of several pollens produce? Would not a forced fecundation act upon the ovary in an extraordinary manner, and changing tho natural relations of the principles, form heterogeneous combinations incapable of bearing sexual organs?

All these queries were presented to my mind in a manner so favorable and seductive that I made no delay iu preparing experiments to throw light upon thcm. Their results have beou so satisfactory that I have been able to draw therefrom a theory which hasscrved as the basis of my classification of orauge trees. I shall give an explanation of them.

Abt. VIL—Experiments in artificial jicundutton.

Experiment P.—I chose a number of plants of the Asiatie, ranunculus, of simple flower, and of different colors. I put each one in a vase, aud placed them in as many different windows, separated from each other. I fecundated the flowers of one-half these plants with the pollen of each other, but left the other half undisturbed. The following results were obtained: The seeds of the flowers fecundated as aforcstated produced roots of which some gave double flowers, others semi-double, and the greater part only single flqwcrs. The plants not fecundated grive only

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