Agricultural Journal, 7(4): 321-342 (1823)
SOME NOTICE OF THOMAS ANDREW KNIGHT, ESQ. PRESIDENT OF THE HORTICULTURAL SOCIETY OF LONDON.
HIS EXPERIMENTS AND PRESENT TO THIS SOCIETY.
[By the Corresponding Secretary.]
If any apology could be necessary for the brief and imperfect notice which we are about to take of one of the most distinguished cultivators of the age, of a man who has done as much to enlarge the boundaries of theoretical agriculture, and horticulture, as any man living, while he has at the same time done more than any man with whom we are acquainted to advance that science practically, it will be found in the kind expressions of his regard for our country, and his generous exertions to make us partakers of the improvements he has actually effected in his own. To those who may be disposed to consider horticulture as less interesting and less within the province of this society, we would observe (at the hazard of repeating and reinforcing the remarks we made in first article) that it is precisely the branch of agricultural industry which in our country needs the most attention. It is the one in which we are most deplorably deficient. So long as we were surrounded with Indian neighbours, and our crops were so precarious that our only anxiety was to procure bread corn sufficient for subsistence, it was natural, that we should be indifferent to the rich profusion of vegetables and fruits, which nature has provided for our luxurious enjoyment. In this particular, we can without blushing, compare ourselves with the European nations at a period not far distant; and when we learn that the water-cress was the only sallad for the royal table in the reign of Queen Elizabeth, we may not be surprised at the scanty supply of our own tables, fifty years since. But we are past that age, and we see no reason, why we should not have the finest melons of Persia which we can grow in the open air, while a Russian Prince will enjoy them in spite of nature, by expensive hot-houses heated by steam. We feel only a sentiment of humiliation, when we reflect, that countries which the sun never heats, produce the most luxurious fruits, while our sun wastes its powers in many parts of our country on a rich and productive soil, which is applied, in most cases, to the raising of the coarse vegetables, which our Indian predecessors bequeathed to us. In this remark, we refer only to vegetables for the table, not to our invaluable staple articles.
Much has undoubtedly been done in the vicinity of our great towns, and horticulture has within our memory made a progress equal to our growth and improvement, but much remains to be done even here, and the inhabitants of the country at large may be considered as to horticulture, in a state of nature, excepting always some liberal, and spirited individuals who have made horticulture their study. After the provision for the support of life, come our comforts and rational luxuries, and if these can be obtained, without neglecting the more substantial and important articles, it is our interest to procure them. This is our apology for introducing the character, discoveries, and exertions of Mr. Knight. He has devoted his life to the investigation of the physiology of plants, and it has been his rare merit, to submit his theories to the best test, that of experience. He no sooner settled a principle than he undertook to shew its truth by actual experiment, and to prove its importance, by applying it to the practical amelioration of horticulture. He early announced, that individual varieties of plants have their limited age; that although by culture, and in favourable circumstances, they may survive that age, they generally after that period decline and become weak, and of course unprofitable. With respect to the potatoe, he ascertained with as much precision as the nature of such a subject will admit, that the specific varieties do not last in perfection more than fourteen years. No observing man in any country could doubt, as to the temporary duration of the varieties of this vegetable, however he might question the accuracy of the precise limits assigned by Mr. Knight. There is not a single variety of the potatoe now cultivated with us with which we were familiar thirty years since; and within twenty years, we have known several sorts which were invaluable, gradually run out; and this too, not from any want of attention, but from the impossibility of raising them. We will mention two sorts, as examples, the round cranberry potatoe, better than any now in market, a great bearer, excellent in the spring after other potatoes become flaccid and watery. We continued to raise them, till they would not produce double the amount of the seed put in. They are now extinct. Another was a blue potatoe, with white spots—a delicious variety, brought from England direct, and also from Connecticut. For the last four years, it has become extinct. Some persons are deceived by appearances. We have always white, potatoes, and they think them the same, but the varieties are infinite, and are constantly changing. The long reds, called the River Plate potatoes, have essentially changed their character, and ten years hence we shall no longer see that very valuable variety. So far our experience fully supports the theory of Mr. Knight.
Mr. Knight, if not the first to suggest the mode in which the sap circulates in vegetables, was, we are persuaded, the first who proved it to the satisfaction not only of men of science, but of the most incredulous and ignorant. Some of his early experiments were made on plants whose parts are transparent. He took, we believe, the Balsamine, or "Touch me not." He watered it with a coloured fluid. He saw that the fluid passed up in the central parts of the plant, made its way into the leaves and having coloured them, it returned by the bark which was the last affected. For the information of those who have not attended to the structure of plants, it may be remarked, that they consist of an external covering which is generally very thin, called the Cortex; of a softer substance, which is usually confounded with the other, called Liber; of a white portion, called by botanists, Alburnum, and commonly known as "sap wood;" and the Heart-wood, which in more durable trees is usually much the most dense and solid. Mr. Knight maintained that the sap ascended in the Alburnum and descended in the bark, or between the bark and the Alburnum, where it made its deposit of new wood. This theory was not without its practical value. It explained the reasons of the fact of the destruction of trees by decortication or a too great removal of the bark, if accompanied with such wounds in the alburnum as to prevent the formation of new bark. It was known before, that you might cut off half the top and half the roots of a tree and it would still flourish, but if you should make a wound of one inch wide through the bark, and into the Alburnum, the tree inevitably perished. His theory led to various experiments, founded upon its undoubted truth. Mr. Williams of Great Britain applied it to the early maturation or ripening of grapes, by taking off the bark to the extent of a quarter of an inch in width; it was found that the sap was impeded in its descent, the parts above became larger, the fruit swelled and ripened earlier and was more large and fine. This experiment was repeated in this country by the writer of this article, and its success was so perfect, that nothing could be said against the theory by those who were eye witnesses of its extraordinary effects. Another consequence followed from this discovery of Mr. Knight. If fruits can be hastened to maturity, and enlarged and improved by partial and prudent and judicious decortication, why, it was asked, may it not be applied to the bringing trees earlier into bearing, than by the ordinary process of nature? This it was said would, necessarily be the effect of detaining the sap preternaturally in the branches, and thus forcing the plant to produce blossom buds instead of leaf or branch buds. It was before well known to gardeners, that any thing which checked the growth of a fruit tree, hastened the production of fruit. It was reserved for Mr. Knight to shew the causes, and to submit the whole process to rules as certain as are known in any other branch of natural science. In all, we are stopped at certain points, when we rashly venture to penetrate the great secrets of nature, but this is no reason why we should not search as far as we can find intelligible explanations and facts.
Perhaps it would be satisfactory to our readers to have experiments at home stated to them, in support of Mr. Knight's theories, and we trust that due credit will be given to our statement of actual experiments, especially as nothing would give us more pleasure than to afford any cultivator the most perfect satisfaction as to the accuracy of these statements, if he will do us the honour to call and examine the subjects of our experiments.
On two orange-trees from St. Michael's, which had never borne fruit, though we had had them many years, we practised decortication, taking off a ring of the bark of half an inch in width. In the following spring, this year, the gardener expressed to me his surprize, that those limbs were literally loaded with blossoms. He had not been in the secret. We pointed out to him the decortication or ringing, or as we say, the "girdling," and it was found, that while every other part of the tree was without blossoms, those which were operated upon were far too greatly covered with them. In this case we committed a mistake. The orange-tree puts forth only once in a year ordinarily in our climate, or under favourable circumstances, twice. Ringing or girdling should only be executed when the sap is in the greatest possible degree of action. These limbs are not healthy, and we fear will not hold their fruit, but the experiment shewed the principle in its clearest light. The general rule is, to girdle when the tree is in its most rapid state of growth, to make the decortication or ring larger or smaller according to the vigour of the plant, but so little in all cases as to enable the tree to close the wound during the same season. We made a similar experiment on a flowering plant, the beautiful Passiflora Alata, and we threw it by this process into flower, at a season in which it never flowers in the ordinary course of nature, that is, in the month of August. Its usual time of flowering with us, is October and April.
But we proceed to experiments out of the green house, within the reach of all cultivators. We tried this plan on 20 young pear trees, on one, two and three branches—trees, which have been grafted from 10 to 12 years, without giving fruit. The spectacle on so extensive an experiment, is really interesting and instructive, as shewing the power of human art over nature. A single branch in a tree is at this hour, when we are writing, absolutely snowy white with flowers, while every other branch on the same tree is as barren, and unprolifick, as it had been every preceding spring, when it had blighted our hopes. We sported very much in our experiment? On some trees, we girdled one, and on others 2 to 5 branches, but the experiment is so perfect, that before you reach the tree, you can decide precisely which were and which were not girdled. The same experiment was made on plums, with equal success.
Let us here, however, check any disposition which may have been excited in favour of this mode of hastening early bearing, by saying, that Mr. Knight, from whose theory the experiments have been derived, is opposed to it on a general scale. He thinks it will shorten the longevity of the trees subjected to it; that it is adverse to the course of nature, and is only justifiable when you wish to be certain, whether the trees you have bought or grafted are really what you supposed they were, or when you have new seedling fruits, to enable you to ascertain some years earlier their qualities, in order to decide, whether you should reject them or not. I do not carry my apprehensions so far (I say it with great diffidence) as this learned cultivator. The effect of judicious girdling is nearly the same with grafting; that produces a similar interruption of the sap, a callous is formed between the original stock and the graft, and yet we see the branches continue productive, and enjoy excellent health. No doubt great discretion and prudence should be exercised in the application of it. Mr. Knight has adopted other modes of hastening the early production of fruit on young trees. Some he raises in pots and boxes, others he bends down either to an horizontal, or even to an anti-perpendicular form, if we may be allowed a novel expression. The sap is thus impeded in its course, and Mr. Knight has shewn, that the principle of gravitation is as operative in the fluids of vegetable life, as in others. The effects are nearly the same as those of girdling, producing earlier bearing.
But these are but a part of Mr. Knight's labours and services. Following up the Linnaean theory of the sexual system of plants, (or to speak in language better adapted to all classes of readers,) proceeding upon the well established fact, that certain parts of the flower, called Anthers, produce a dust called Pollen, which is indispensable to the fertilization of the germ or fruit, a fact known to be true, before Linnaeas existed, but which never received perfect confidence, till he demonstrated it. Mr. Knight has devoted 35 years of his life to the practical application of this theory, which he has not only demonstrated by hundreds of experiments, but he may be said to have created many new and valuable varieties of fruits hitherto unknown. He has obtained new varieties of the pear, the apple, the grape, the plum, and the strawberry. He has demonstrated, that we can correct the defects of one variety of fruit by another, by introducing the farina of a pear for example, which has too much austerity or acidity, into the flower of another pear, which has too much sweetness, too insipid a sweet, you may give to the new product a taste and flavour, which may he perfectly agreeable. So it has been ascertained by Mr. Knight, that by the same process, a fruit which is defective in vigour, which bears with great reluctance a cold climate, may, by intermixing it, or coupling it wills another tree of the same species of a hardy character, acquire the vigorous constitution of one of its parents, and still retain the excellent qualities of the other parent. There is, indeed, no end to the changes which have been produced by Mr. Knight and others, not in fruits, but in flowers, by this process. We are aware, that this statement, to those who are ignorant of his exertions and success, may seem to be extravagant; but we can affirm, that he has done more to improve horticulture than any person of whom we, in this western world, have any knowledge.
These remarks were intended as an introduction to a notice of the efforts which Mr. Knight has generously made to communicate to America some of his improved fruits. In 1822, I had occasion to write to Mr. Knight to procure the last numbers of the Horticultural Transactions, for the College; he replied to my letter in the most friendly manner, appeared to be highly gratified with opening an intercourse with our country, expressed his strong attachment to it, his disgust at the libels on our country in some of the presses of Great-Britain, and his intention to send to us the best new fruits which the late improvements had introduced; declaring at the same time, that though he should confide them to my care, it was under the full belief and expectation, that I should disseminate them as extensively as possible. I need not say, that he could not have given me a charge more agreeable; and that without the smallest regard to personal interest, I shall circulate as rapidly as possible, by buds and scions, every variety of fruit he may send. I shall consider myself steward for the public—but I ought to remark, that Hs he sends but one individual specimen, the progress must be slow, and that I must exercise a discretion in giving scions and buds to such persons as will be most like to take good care of them; but l shall do it in all cases on the express condition, that the same freedom of circulation shall be practised by all.