American Pomology

DEFINITION OF. OBJECTS. EARLY FRUITAGE. DEFINITION OF TERMS.

DWARFING STOCKS. OTHER MEANS OF DWARFING. DWARFS AND STANDARDS.

PYRAMIDS OR CONICAL. ESPALIERS. LAYING BARE THE MAIN ROOTS IN SUMMER, TO DIMINISH THE VIGOR OF THE TREES. REMOVING A PORTION OF THEM. ROOT-PRUNING. TRANSPLANTING. EUROPEAN ESPALIERS AND WALL FRUITS. DU BREUIL'S CORDONS. CROWDING, AS A MEANS OF DWARFING. PINCHING, TWISTING, AND FRACTURE. FIELD'S PEAR HEDGES. OUR CLIMATE DOES NOT REQUIRE THESE MEANS OF TORTURE.

FACILITY OF PROTECTION MAY RENDER THEM DESIRABLE. GENERAL INTRODUCTION OF QUINCE-DWARFED PEARS IN THIS COUNTRY. MANY FAILURES. SUCCESS DEPENDS UPON CARE. FRENCH SUCCESS. CHINESE.

UNCONGENIAL STOCKS. IMPERFECT UNION. PINCHING. HIGHEST PERFECTION OF THE ART OF HORTICULTURE. EQUALIZE THE FLOW OF SAP. NATURALLY FLOWS TO HIGHER PARTS AT EXPENSE OF LOWER, MAY BE REGULATED BY Tr.i.m.m.i.n.g. BY DISBUDDING. BENDING DOWN. PINCHING THE STRONGER, AND ENCOURAGING THE WEAKER. ILl.u.s.tRATION IN THE STRAWBERRY. DWARFING THE APPLE. PARADISE STOCK. THE DOUCIN; UNFIT FOR ORCHARDS. ROOT-PRUNING. HOW IT OPERATES. TIME TO BEGIN. HOW TO BE PURSUED. SEASON FOR. EXPENSE. ROOT-PRUNING PLOW.

Dwarfing consists in so controlling the growth of plants as to reduce the natural size of any of our fruit trees, and bring them within comparatively narrow bounds. The objects of dwarfing are to enable us to plant a large number of specimen trees, or of varieties upon a small piece of ground, or to have small trees beside the alleys of our gardens. Such plants are also well adapted for growing in pots, or in the borders of an orchard-house. It is claimed for dwarfed trees, that they are more prolific than those which are worked on free stocks, which are often erroneously called standards, and it is also a.s.serted that these dwarfed trees will bear sooner and produce finer and larger fruit.

The terms used may as well be explained at once. When we speak of dwarfing stocks, we mean such as are so uncongenial as to check the wood-growth; and thus, while producing smaller trees, they have a tendency to early fruitfulness if properly managed. But this condition may be superinduced by other means than these. Hence in speaking of dwarf pear trees, it does not follow that they have been worked on the quince or other uncongenial stock. A dwarf tree, of whatever kind, is simply one that has been caused to a.s.sume diminutive proportions.

Dwarfing stocks are contrasted with free stocks, or those which would have attained the full size of the species, and which, when grafted, produce large trees. These are often mis-called standards, when contrasted with those that have been worked on the quince, or other dwarfing stock. Whereas, the trees propagated on free stocks, may also be dwarfed, by means that will be presently detailed; and the term standard refers really to the mode in which the training of the specimens has been performed. Those which are trimmed up as orchard trees are usually treated as standards, and are said to be trimmed to standard hight. Those branching at a lower point are called half standards. Those which are branched so low as to conceal the stem of the tree, and in which the limbs are so well managed that the lower ones are always the longest, and those above them gradually contracted to the point at the top, are called pyramids, or more properly conical trees. Whether dwarfed or not, trees may be trained in a variety of forms, such as the columnar, sometimes called the _quenouille_; the vase or goblet form may be given them, or the parasol shape, and they may be made to a.s.sume the form of a fan or other mode of extension laterally, when trained upon a wall or espalier frame, as may be seen in the ill.u.s.trations given by Du Breuil; but it is seldom that our gardeners are willing to bestow the care and attention necessary to produce these results.

The vertical and oblique _cordons_ represented and recommended by Du Breuil are very attractive, and admirable methods of training and dwarfing fruit trees, and of crowding a great many into a small s.p.a.ce.

His method of making an edging to the fruit-border with dwarf apples, inarched together so as to form a connected tree for its whole length, is a capital ill.u.s.tration of the control we may exercise upon vegetation.

Standards and pyramids are often trained as weeping trees, for the sake of gratifying the fancy of the cultivator, and with a view of bringing on that early productiveness which results from the check of the upward current of sap that is incident to such a mode of treatment. This is really a kind of dwarfing so far as it goes, and if commenced early in the life of the tree, it may become very effective, especially when combined with other means of reducing the growth.

These are formed by arching the branches, tying their tips to a ring of wire or hoop secured near the ground, or simply by fastening weights to them sufficient to keep them in the desired position, and by tying the upper limbs to the lower ones. As is well known, the sap flows most readily toward the shoots that occupy a vertical line; it will be seen that its ascent will be seriously r.e.t.a.r.ded in those that are bent, and their vigor will be diminished, and fruit-bearing will be promoted. This process must not be continued too perseveringly, lest the tree become exhausted by over-production.

Du Breuil recommends laying bare the princ.i.p.al roots of the tree in the spring of the year, so as to expose them for the most of their length, and leaving them in this condition during the summer. This exposure of roots to the sun and air diminishes the vigor of the tree, and hence it tends to the production of fruit. He also recommends the removal of a part of the roots in the spring, and replacing the earth; considering this a more energetic operation than the preceding, he advises caution, lest we injure the tree. This is simply root-pruning, a plan that has been pretty thoroughly tested in this country, where, perhaps, its beneficial effects are more needed than in any other, and where we shall even find it advantageous to have recourse to mechanical means for its performance in large orchards by horse-power, as will be set forth in another place.

A very successful method of obtaining the desired effect of dwarfing, which is early and abundant fruiting, consists in transplanting the trees in the autumn; this should be done very carefully, so as to preserve the roots from mutilation as much as possible. The effect of this will be to check the wood-growth the ensuing summer, and fruit-buds will be formed, for it is well known that these two opposite conditions of plant life are complementary the one to the other, and while we always desire to see them both proceeding together in a healthy tree, the wood-growth must have been moderated before we can expect to receive any fruit.

The French and English excel us in training upon walls and espaliers, and we may willingly yield them the palm; since, in this country, it is rarely necessary to incur so great expense for the production of good fruits, and as a means of dwarfing our trees, it is more expensive and requires more skill, care, and watchfulness, than other methods of producing this effect. Espalier training, however, affords the most beautiful opportunity for the ill.u.s.tration of many of the important principles of vegetable physiology, but it should never be undertaken by any one who is not familiar with these, and at the same time willing to exercise great patience and perseverance in their application to the subjects under his control. No blind pursuance of the abstract rules of the art can enable the mere routine gardener to become a successful grower of espalier trees. The modes of training are various, to suit the whims and necessities of the artist. Trees are fastened directly to the walls, or to trellises of wood or of iron, that are placed at a little distance from the masonry, or they may be entirely independent of any such structures, and exposed to the air and light freely on both sides. The trellises may be either vertical, or inclined. The limbs may be made to issue nearly opposite to one another, and be trained horizontally in two directions, with successive stages to the top of the wall or trellis, or they may be trained in a fan shape, with various modifications of what M. Du Breuil calls the _palmette_ form. And a simple modification of this method of dwarfing may be made with some varieties of fruit, by training a single stem horizontally within a foot of the ground, as a border or edging between the path-ways and the cultivated ground.

The favorite method of training in France, at the present day, appears to be that called the _cordon_. This may be either the vertical or inclined. In this kind of espalier, the trees are dwarfed by crowding them closely together, and by successive pinching and other mutilation, such as bending and even breaking the shoots, which results in early productiveness. The trees are planted sixteen inches apart, and are trained to single stems, and so treated as to be furnished with the requisite number of fruit-spurs on their whole extent. This is quite a new application of principles, and one which is rudely imitated by Mr. Field's pear hedges, which, however, bear but little resemblance to the elegant cordons of Du Breuil beyond that of dwarfing by crowding and pinching. We are told that among the many advantages of this method, are the diminished time required to cover a wall or trellis with fruit, and the greater facility of replacing a dead or defective tree, which, in the usual espalier methods, is a very serious matter, requiring several years for its restoration and the production of a crop.

We are so blessed, in most parts of this country, with soil and climate that are well adapted to the production of fruit in the open field, upon st.u.r.dy orchard trees, that there is less necessity for introducing these elegant methods of pursuing the fine art of horticulture; and yet there are reasons in the uncertain climate of our winters, why these plans of training and dwarfing should be pursued by those who have the talent and the means for doing it. Until within a few years, there were not many dwarfed pear or apple trees in this country, and they were confined chiefly to French gardens and to the establishments of the wealthy. But since their more general introduction, immense numbers have been propagated and planted, and extensive orchards, particularly of dwarfed pears, have been set out with a view to profit. Some of these have been eminently successful, others are failures; the results will very much depend upon the amount of care which may be bestowed upon them.

The French have long practiced the dwarfing of certain varieties of fruits, and have been very successful in their results; but that wonderful people, the Chinese, excel all others in this branch of horticulture, for which they display a remarkable talent.

DWARFING BY UNCONGENIAL STOCKS.--The usual mode, which is literally a partial starvation of the tree by limiting the supplies of crude sap, consists in the use of uncongenial and dwarf-growing stocks, upon which the desired varieties are budded or grafted. These are, for the dwarfed pear, either Quinces, Thorns, the Mountain Ash, or the Amelanchiers; for the apple, the Paradise and the Doucin varieties

To produce a dwarf by grafting on an uncongenial stock, this should be so uncongenial as to form an imperfect union, which checks the downward circulation; the sap that has been elaborated by the organs of the scion is thus kept above the junction of the two woods, and, being so checked, the result is the early formation of fruit-buds, and a premature fruitage of the trees results in a direct proportion to the incompleteness of the union of scion and stock. This is often so very imperfect as to be very easily ruptured, the grafts are often broken out by a very small force being applied to them, sometimes even the weight of the fruit is sufficient to effect a separation, and an examination of the rupture will show how very slight or imperfect the union between the parts has been; in other cases, however, it is difficult to trace the fibres of wood-growth that belong respectively to the stock and to the scion, even when these have been so different as pear and quince, or plum and peach.

It is also considered desirable that the roots of the stock should be small and fibrous, and not long, naked, and straggling; the former will furnish the crude sap in more limited amounts, and are less likely to produce an excessively rampant or luxurious growth in the scion.

Many persons have been disappointed in the Mahaleb cherry, which has been reputed to be a dwarfing stock. It is found, that without the application of other means, the so-called dwarfed cherries grow as freely, at least in their early years, as those worked on the free stock, known as the Mazzard cherry. They will never make such large trees, however, and those who would enjoy dwarf cherry trees, should combine the different methods of producing the result.

BY PINCHING.--There are other means of producing the desired effects of dwarfing and early fruiting, which should be mentioned. These consist in systematic efforts to curtail the development of the wood-growth, by judicious pinching, of the tips or points of the branches, and to prevent the rambling of the roots by root-pruning.

These it is designed now to examine. Pinching is practiced in the green-house with the happiest effects, and it results in the production of the most perfect form of the plants, and most abundant display of flowers. The constant check which is thus given to the wood system, causes the sap to seek new outlets, and instead of the one limb into which it had been flowing, and causing it to be developed; its flow is now directed to the other buds along its course, which presently burst out into lateral growths, none of which are so strong as the first, and these are induced to change the character of the buds so as to result in the production of flowers and fruit.

This system applied to fruit-trees has been most thoroughly carried out by the French, and is admirably described and ill.u.s.trated by Du Breuil, in a work called _Scientific Culture of Fruit Trees_, and reproduced in our own language by Wm. Wardle, an English gardener and orchardist of high reputation.

It is not to be expected that in this country, where fruits are so easily produced, we shall soon reach such a point of horticultural practice as to lead us to the adoption of the European system of walls and espalier training, but we shall do well to watch the application of the very important principles involved in their practice, since these may be applied to our orchards with manifest advantage. In reference to the form and management of trained trees, it is established as an axiom that their permanency is dependent upon an equal diffusion of the sap being kept up throughout the whole extent of their branches. This occurs naturally in all trees, because they develop themselves in the forms natural to them, but in our gardens and orchards we make our trees a.s.sume unnatural forms. The sap flows to the highest parts by a law which is well known, though not so well understood; as a consequence, the lower branches do not receive their needed supplies, and being smothered by those above them, they eventually die and decay, leaving a naked stem supporting a top, or the common form of the natural tree. To maintain the shape we desire--be this the pyramid, the vase, or the espalier of whatever kind--certain operations must be performed from time to time, as the conditions of the tree may indicate.

Among these, Du Breuil advises to prune the strong branches short and allow the weaker ones to grow long, and thus to restore the balance.

This may be done at the spring pruning, and also at any time during the growing season, when it may be necessary to check excessive growth at any one point: and upon this principle depends some of the most important practice of the summer pruning of our vineyards. The sap flows towards the leaves, and by removing them from one part, and leaving a preponderance upon another, we change the direction of its flow. As the strongest flow is toward those parts that are in a vertical direction, we may also check this tendency, or encourage it, by altering the position of the branch, as is done in the vineyard by tying up the canes we wish to have developed, and depressing the laterals with their fruit; so in a tree, we may depress the shoots which are too strong, and elevate those that are weak, to produce the desired effect. We may also greatly diminish the flow of sap to a strong branch by removing early all its useless buds; this is a sort of premature pinching to be sure, but when we consider the powerful influence exerted by these organs as centers of vitality, we can realize their attractive force in drawing the sap towards them. After the production of the full number of shoots upon the weaker branch, if the foliage continue to predominate upon the stronger shoot, it may be partially removed by early pinching, or cutting through the petioles, not by tearing them off; and as late as possible, remove the surplus and useless shoots from the weaker branches, which were at first needed to encourage the flow of sap in that direction.

The true pinching of the young laterals, or new shoots, should also be done as early as possible to keep them in check on the strong branches, while the same operation may be delayed on the weaker, from which we should remove only those that will be supernumeraries. M. Du Breuil also recommends the stimulation of the weaker limbs, by bathing all the green portions with a solution of sulphate of iron, made by dissolving twenty-four grains in a pint of water. This should be applied in the evening, when it is absorbed by the leaves, and acts as a powerful stimulant.

It is a well established principle, that the chief growth by extension will be made by the terminal bud, and this should either be removed by cutting back, or left upon the limb, according as we desire to grow our wood; if extension of the shoot be our leading object, all the lateral buds must be subordinated. So also, it is well known, that all circ.u.mstances, which r.e.t.a.r.d the circulation, are followed by a diminution of the wood-growth, and by the development of flower buds.

The culture of the strawberry affords one of the best ill.u.s.trations of the benefits and effects of pinching. The runners of this plant may be viewed in the light of wood-growth, or the increase of the plant by extension; even though these slender threads are not permanent, and they only serve to convey a bud to a distance from the parent plant, and place it under favorable circ.u.mstances for the formation of a natural layer. They are but annual productions, and hence there is no considerable deposit of woody matter, as in the limbs of trees, but they are thrown out from the parent plant just like woody branches, and are so much substance withdrawn from it, which, if retained or thrown back upon the plant, would have resulted in an enlargement of the main stem of the strawberry plant, and in the development of buds upon the crown, which become stored with the proper juices that result in the production of more abundant blossom buds. The result, however, is so admirable an ill.u.s.tration of this important element in the management of permanent and woody fruit-trees, that we may well look at an herbaceous plant, be it even so humble an individual as the prostrate earth-berry, as our ancestors called the delicious _Fragaria_.

DWARFING THE APPLE

Apples are generally dwarfed by working them upon the French Paradise stock, which is a very diminutive tree or bush, seldom rising more than a few feet high. This is the true stock for those who wish to indulge in the luxury of dwarf apple trees. Such are very appropriate for the small garden, or for the specimen grounds of a nursery establishment, and they sometimes make beautiful objects in the lawn or among the shrubbery, but they are wholly unsuited for orchard planting, as many a poor deluded purchaser has found out to his sorrow, a few years after having been beguiled by the smooth-spoken tree peddlers, who have sold many thousands through the country to farmers to plant as orchard trees.

There is a more vigorous stock which has been used for the same purpose, but it possesses much less dwarfing power. It is called the Doucin, or English dwarfing stock. This, however, exerts so little of the dwarfing influence, that at the end of eight or ten years the trees are generally about as large as those worked upon free stocks; but it happens unfortunately that early fruitage, the great object of dwarfing, is not attained by their use, for they will not have produced any more fruit than the common trees similarly treated.

BY ROOT PRUNING.--Among the many valuable hints which horticulturists have received, with the beautiful flowering and other plants, from our antipodes in the "Flowery Land," none has been of greater value than the practice of root-pruning. In this art of dwarfing even the large forest trees by mutilations of the roots and by other means, this curious people excel all others, as has frequently been stated. In Europe, and in this country also, root-pruning has been extensively practiced with the effect of partially dwarfing the trees, but more especially with the object of inducing prematurely the fruitfulness we so much desire, and which is a natural result of the diminished supplies of crude sap furnished by the contracted roots of a tree that has been treated in this manner. The balance between the wood-growth by extension, and that which results in fruitful spurs is sooner established, and the sap is directed to the formation and support of the fruit.

We should not commence the application of this severe treatment until our trees have been allowed to establish themselves firmly in their stations, unless we desire at the same time to produce decided dwarfs by means of root-pruning. In this case the treatment may be commenced in the nursery itself; the stocks should be transplanted once or oftener before being worked, and the young trees should be moved annually, which will so shorten the roots as to make them a ma.s.s of fibres, occupying the whole soil close about their main divisions, and the subsequent removals can then be easily effected, with but a slight check to the tree, which becomes furnished with fruit spurs at a very early period of its existence, instead of its requiring years to reach its natural period of fruitfulness, as is the case with some varieties, particularly of the pear.

As generally practiced, however, root-pruning is postponed until the trees have made a free and vigorous growth, and have become well established in their stations. Then if the growth be too vigorous, and there do not appear any indications of the formation of fruit spurs, as is often the case in the fertile soils of the West, our impatient orchardists complain of the barrenness of their trees, and seek a remedy in root-pruning. This is generally performed with a sharp spade, with which a trench is dug in a circle around the tree. The excavation should be deep enough to reach all of the lateral roots; these are generally within a foot of the surface. The ditch need not be much wider than the spade, and the soil can be thrown back at once, but all the roots should be severed, if we desire to produce the effect of checking the wood-growth. The diameter of this circle will depend upon the size and vigor of the tree to be operated upon. As a general rule, it may be made in the proportion of one foot to each inch of the tree's diameter. The work may be done at any time after the spring growth has begun to harden, or during the autumn and winter, and until the buds are about to break in the spring. The operation is wonderfully conducive to the end we have in view, and we often see a vigorously growing but barren subject, transformed in a single season into a fruitful tree, covered with blossom-bearing spurs that are full of promise of delicious fruits. In some varieties, however, these fruit spurs require more than a single season for their perfection.

Now it may be objected that this labor will be expensive, and so it is, as all hard work with the spade must be; but what of that, when we consider the happy results that ensue in golden harvests. But it has been suggested that this labor may be performed by farm machinery, using a strong plow, or rather a sharp cutter attached to a plow beam, and drawn by a powerful team at the requisite distance on either side of the rows of trees, and in directions crossing each other at right angles. This, of course, like all mere mechanical applications, must be uniform, whether the necessities of the trees be equal or not; whereas, by hand-labor, we may vary the distance at which the roots are to be cut, according to the vigor and size of the trees demanding the treatment.

This topic will be again referred to in the chapter on Pruning, where also it will be necessary to recur to the subject of Training, which was incidentally alluded to in connection with Dwarfing.

CHAPTER V.

DISEASES.

DIFFICULTIES IN THE OUTSET. WHAT CONSt.i.tUTES DISEASED ACTION. NO a.n.a.lOGY TO ANIMAL SICKNESSES. CONGENITAL DEFECTS. DEBILITY.

DEFICIENT STRENGTH OF FIBRES. DEFECTIVE FOLIAGE. IMPERFECT AND REDUNDANT BLOSSOMS. THE CIVILIZED AND CULTIVATED PLANT MAY BE ABNORMAL ALTOGETHER. UNSATISFACTORY ACCOUNTS OF DISEASES IN PLANTS. LANKESTER'S CLa.s.sIFICATION CONSIDERED. EFFECTS OF THE EXCESS OR PAUCITY OF MOISTURE, HEAT, AND LIGHT. MODE OF ACTION OF FROST. INJURY RATHER REFERRIBLE TO THE CONDITION OF THE CIRCULATION THAN TO THE DEGREE OF COLD IN MANY HARDY PLANTS.

INFLUENCE OF THE SOIL. LIGHT THE GREAT STIMULUS, ITS WITHDRAWAL SUSPENDS HEALTHY ACTION. ITS SUDDEN RESTORATION CAUSES DEATH BY SUN SCALD. INJURY BY SUNs.h.i.+NE IN WINTER. POISONOUS GASES.

MIASMATA. POISONS IN THE SOIL. PARASITIC PLANTS, EPIPHITES, FUNGI, PEAR BLIGHT. VARIOUS THEORIES. WHAT WE KNOW, AND WHAT WE DON'T KNOW. TREATMENT. ROOT PRUNING SUGGESTED. SATISFACTORY RESULTS. MILDEW BLIGHT IN PEACH AND APPLE. TWIG BLIGHT IN APPLE AND QUINCE. THE APPLE BLIGHT. BITTER ROT. CRACKED FRUIT. SCAB.

MILDEWS. KIRTLAND'S VIEWS AND SUGGESTED REMEDY. WOUNDS AND INSECTS. NEEDING THE AID OF SURGERY RATHER THAN MEDICINE.

DESTRUCTION OF FOLIAGE BY INSECTS IMPAIRS THE HEALTHY CONDITION OF THE PLANT. RESUME. SELECT HEALTHY TREES OF HEALTHY VARIETIES. EMPIRICAL CHARACTER OF TREATMENT USUALLY RECOMMENDED FOR DISEASED TREES. THE BLACK KNOT. THE ROT AND MILDEW OF THE GRAPE.

In opening a discussion upon the nosology of vegetation, it may be expected that one who had spent many years of his life in the investigation of the diseases of the human family, and at the same time was something of a student of comparative anatomy and physiology, tracing a.n.a.logies between the animal and vegetable kingdoms, should be familiar also with the diseases of plants. Such an antic.i.p.ation, it is feared, will not, in the present instance, be realized. Indeed, the writer feels very much at a loss how to proceed in discussing this branch of the subject, and hardly knows what departures from undoubted health and vigor should be considered worthy of the t.i.tle of disease.

Nor is it easy to trace the causes of the conditions that are generally viewed in the light of maladies. We find the manifestations both in the tree or plant, and in its several parts, and also in the products which chiefly interest us; the fruits themselves, are often deteriorated by what is called diseased action of different kinds. The a.n.a.logy to diseases of animals is certainly not very distinct. We do not find anything like fevers, or gout, or rheumatism, in plants, but we may consider some of their conditions somewhat in the light of dropsies, and plethora or hypertrophy on the one hand, and of anaemia or atrophy upon the other; we may consider canker and the death of some parts of a plant a.n.a.logous to gangrene, and mortification in the animal subject. Then again we find congenital defects in individuals among plants, just as we do among animals. Some are always less vigorous than others, and thus certain varieties seem possessed of a degree of inherent disease that perpetually prevents them from displaying the requisite strength and vigor which we so much desire in our plantations. Certain varieties that, from the size and excellence of their fruits, have attracted the attention of pomologists, are so deficient in health and vigor as to be considered diseased, and are therefore very properly condemned as unworthy a place in our orchards and gardens; others appear simply deficient in the production of some one part, as is ill.u.s.trated by the inferior strength of the woody fibres of some trees, which break easily under the weight of their own fruit, and thus destroy the symmetry of the tree and diminish its productiveness. Others have defective foliage, which is attended by the imperfect performance of the functions of growth, both in the fruit and in the sustaining woody fibres; others again produce defective blossoms with either a redundancy or deficiency of the parts that are necessary for the production of the seeds needed for the perpetuation of the species. When the parts are deficient, the flowers are called barren or infertile. A redundancy or multiplication of parts is seen in double flowers of our gardens, where they are much prized for their beauty, though considered monstrosities by the botanist, and perhaps properly referred to diseased action by the nosologist.

It is evident, that very often the conditions of a plant and its products, which we most highly prize, and towards which all our efforts in its culture are directed, are really departures from the natural and healthful status; in other words, what we covet, is really a state of diseased and abnormal action. With the other secondary objects of occupying and ornamenting the barren wastes of the earth with plants, and thus supplying food to hosts of insects, and to the higher animals, nature also has primarily in view, the production of perfect seeds for the perpetuation of their species, by the plants that are profusely scattered over the globe. Man, on the contrary, often rejects the true seeds as worthless when compared to their juicy fleshy envelopes that const.i.tute his favorite fruits, or the enlarged and succulent roots, tubers, stalks, and leaves, that characterize his garden vegetables and field crops; while in the grains proper he seeks sustenance in the true seeds, which become the object of his greatest care and ingenuity to enlarge, to increase, and to develop, particularly in regard to their nutritive qualities.

Most writers upon the diseases of plants have given us very indistinct notions upon the subject, and have done very little to enlighten their readers; while they have written voluminously upon the unhealthy and unsatisfactory condition of certain vegetables, and have given us most extensive accounts of the treatment by which they propose to remedy the evils complained of, we gather little of the information needed to enable us to understand the true state of the case, or of the causes of the disease, if it is to be considered such. The reader need not expect that he will be more enlightened by this chapter than he has been by the essays to which reference is here made, but he will be led to a consideration of some of the causes of those departures from health and vigor which are considered diseased action, and in this way he may possibly be put upon the track which will lead him to the avoidance of disastrous results. More than this will not be attempted.

Perhaps the most satisfactory account of diseases of plants is that given by Lankester, in which he divides them according to their causes, as follows:

1st--Those produced by changes in the external conditions of life, such as redundancy or deficiency of the ingredients of soil, of light, of heat, air, and moisture.