through soft, newly-forming tissue, and this is what gives the spongioles their peculiar power. They are, indeed, simply the growing points of the rootlets, which are constantly increasing in length, and which in this manner go in search, as it were, of the supplies of food, of which they have exhausted the soil that previously covered their extremities. As this growth continues, the tissue at first formed gradually becomes consolidated, and when it has become hardened it is no longer adapted for absorption in more than a very trifling degree; so that to the newly-forming point of the fiber this power is always nearly restricted.. But in the young plant there is an interesting correspondence in all the portions of the root, for the soft roots, which are first sent down from the seed when it is commencing to grow, are capable of absorbing by their whole surface; and it is only when woody fiber begins to be formed in them that the power is restricted to their extremities.

The knowledge that the delicate fibers, proceeding from what are commonly known as roots, are the true and only organs of absorption, has an important practical application. It very commonly happens (too commonly among nurserymen) that, in transplanting trees and shrubs, where the roots extend a good way into the soil, enough care is not taken to preserve these; and the tree either languishes for some time, until it is able to form new spongioles, or dies altogether. It is seldom that, under the common treatment, a fruit tree will make much progress the first season after transplanting. It is often observed that the growth of roots takes place in the direction best adapted to supply them with moisture; and it has been supposed that plants possessed a kind of instinct or consciousness, which caused them to select this. Many of these cases, however, can be explained without having recourse to such a supposition; and it is probable that, with the advance of knowledge on this subject, the remainder will be also. In fact, to attribute such an instinct to plants, is to place them above the lower animals, which do not exhibit the power of making a choice of this kind. The most common cases are those most easily explained. A plant is in a dry soil, and it sends out its roots into a moister one; or it is in a garden pot, and its roots project through the hole at the bottom into the water which the pan below it may contain, or into the moist earth with which it may be surrounded. Now, this is explained upon the following simple principle: The addition which is constantly being made to the extremities of the fibers takes place in the direction of the least resistance; and when the roots are making their way through a hard, dry soil, the direction of least resistance will be that in which the earth is loosened by the flow of water-toward the source of that moisture; therefore, the growth of the roots will be in that direction.

The same principle has another curious application. Roots have been known to insinuate themselves into the crevices of walls, or even into chinks in the stones themselves, and to burst asunder the walls of these after some time. Now when a root meets with such an obstacle as this in its growth, it is turned aside for a time, and endeavors, as it were, to creep around it. But

should a chink give the opportunity for the new tissue to be deposited without obstacle in its original direction, the root will find its way into it. The fibril will grow by the nourishment sent to it, and by its own absorption, until it can no longer increase without the separation of the walls which confine it; and this is accomplished by the force with which it imbibes fluid, which causes it to distend itself with great violence. This distention is of the same character as that of a piece of dry wood, when exposed to moisture.

For illustration of the foregoing explanations, we present a case of no infrequent occurrence, in which a tree growing on one side of a road sends out roots to a ditch or stream on the other—these roots dipping deep beneath the hard bed of the road, and rising again on the further side. It is evident by the slight percolation of water which will take place along this line, that the roots follow the same course. Many instánces could be given where plants exist in full health and vigor, depending upon the moisture in the atmosphere alone for support. Many of the orchidae (natives of South America) grow with their roots clinging and clustering round the branches of lofty trees, high up in the air, spreading themselves all over the surface, and hanging from thence like fringes to a great depth beneath. The famous banyan tree of the East Indies is a curious example of this kind. The aërial roots spring out from the upper branches, grow down to the ground and into it, they in the course of time becoming stems. One celebrated specimen possessed 350 principal trunks, and smaller stems amounting to more than 3,000.

We have two remarkable plants indigenous to our own State the dodder (Cuscuta), which attaches itself to the stems of the wild artichoke (Helianthus tuberosa), round which it coils. When luxuriant, the dodder gives a strange, weird appearance to the herb on which it grows, covering a large cluster of it with a floating veil of reddish-yellow, leafless stalks. The mistletoe, found in the lower portion of the Neosho valley, grows on the oak and hickory along the river. bottoms. These parasitic plants strike their roots into the bark and wood of the species they grow on, and feed upon their sap.

The grape-vine is another example; aërial roots will sometimes spring out all along the stems. In summer, we find aërial roots at the lower joints of the stalks of Indian corn; these in the course of time reach the ground, and help to feed and brace the plant.

A more remarkable case, however, is where roots direct themselves along a naked rock, to reach water at a distance of perhaps twenty feet. Another, a tree growing near the side of a well has sent down a root through a narrow chink in its side, which root, after descending many feet without subdivision, has thrown out a vast number of fibers as soon as it approached the surface of the water.

These examples serve to show another fact—that it is not in every case that we are to regard the parts of the axis which are above ground as stems, and

those which are beneath it as roots. There is a tree peculiar to tropical climates, called the Pandanus or Screw Pine, in which the roots are always formed in somewhat of this manner. The stem is smallest at its lowest part and it enlarges considerably above; hence it would be very unsteady without some additional support; and this is provided for by the transmission of the roots, not only from the base of the stem, but at different parts of the upper trunk. These roots grow downward in the air, and are provided with a kind of cup, which catches the rain and dew by which they are partly assisted in their elongation; when, however, they have reached the ground, this cup falls off, and their extremities become true spongioles. When they begin to absorb nourishment from the earth, they increase greatly in diameter, and seem like so many assistant stems.

The general fact is, that the root is the portion of the axis which has a tendency to grow downward, toward moisture and away from the light; while the stem is the portion which tends to grow upward, into the dry air, and toward light. This tendency is manifested during the earliest period of the growth of a plant from seed. Two parts always originate from it-one of which, termed the plumule (from its resemblance, when just unfolding, to a little feather), is the rudiment of the stem and leaves; while the other, called the radicle, is the young root. The first of these exhibits from the commencement a tendency to grow upward, and the second a similar tendency to descend.

Roots are ordinarily distinguished from stems, not only by their direction, but also by the presence of the absorbing fibers, and by the absence of buds (which last is so characteristic of the stem), though we must not forget that the roots of some families of plants have the power of emitting wood buds all along the full extent of their surface. The Morello cherry, the wild plum, the poplar, the yellow locust, the double flowering almond, the blackberry, etc., are familiar examples. In general, however, the stem possesses the power of sending out root fibers from any part; as is shown by cutting off a slip from a branch and sticking it in the ground, or by bending down a shoot and layering it. These, if properly attended to, will form roots, and soon become new plants.

The wide-spreading roots of a forest tree do in reality consist but of bundles or collections of such fibers, strengthened by woody structure resembling that of the stem, and arranged in the same manner. The spread of the roots from the stem is usually greater than that of the branches; so that the rain which is prevented by the latter from falling direct upon the ground, is directed just to that part through which the root fibers are distributed, ready to suck it up.

The force with which the roots absorb fluid is very considerable. We note this when the sugar-farmer taps the maple, and see many gallons of sweet sap pour forth in a few hours; or when the cane of a grape-vine is cut through when the sap is ascending, a large quantity will flow out, and con

tinue to do so for some time. If a piece of bladder is tied over the cut, it will soon distend with the fluid, and in a few hours will burst.

The question then arises: By what power do the roots thus absorb and force upward through the stem the moisture of the surrounding soil? The conditions requisite for this action are two fluids of different densities, separated by a partition of a porous character. This we find in the roots. The fluid in the interior is rendered denser than the water around by the presence of the substances secreted by the cells, and the spongiole supplies the place of the partition. Thus, then, as long as this difference of density is maintained, the absorption of fluid may continue. But if the rise of the sap is due to the action of an inward flow, there ought also to be a flow outward. This is found to take place; for if a plant be grown with roots in water, the fluid surrounding them is soon found to contain some of the peculiar substances they form, and which are contained in the cells of the plant. Thus a pea or bean would disengage a gummy matter; a poppy would communicate to the water an opiate impregnation, and a spurge (Euporbia) would give it an acrid taste.

Thus we see how beautifully and how simply this action, extraordinary as it seems, is accounted for, when its whole history is known, on principles which operate in other departments of nature. It may be asked, Why should not the inward flow take place when the roots of a dead plant are put in water? This question may be answered by another: Why does the wick of a lamp suck up oil only when it is lighted? The answer to both is, that it is only when the fluid already absorbed is in some way removed that absorption can go on. In the latter case, as fast as it is withdrawn by combustion, the lower part of the wick raises it by capillary attraction. In the former, as fast as the fluid is got rid of by exhalation from the leaves, the inward flow will keep up the supply; but if the demand is suddenly checked, (as when the plant is withdrawn from the influence of light, or its vitality is destroyed,) there is no room for any additional fluid within the system, and the absorption is checked also. When the upper part of the stem is cut off, the sap will continue to rise by the force of the inward flow in the roots, so long as the fluid within is of greater density than the fluid without. But that will soon cease to be the case; the action of the leaves being destroyed, there is no loss of fluid to keep up the force. These two causes, then-the absence of any demand for sap in the leaves, and the cessation of the condition necessary for the maintenance of the inward floware quite sufficient to account for its absence in the dead plant; and its performance soon becomes impossible for another reason-the decay of the soft tissue of the spongiole, through which it is performed.

Surprising as it may seem, we may as well state it here, that the roots of plants appear to have a certain power of selection, some of the substances dissolved in the fiuid which surrounds the roots being absorbed, and others being rejected. Thus, if a grain of wheat and a pea be grown in the same

soil, the former will obtain for itself all the silex, or flinty matter, which the water can dissolve; and it is the deposition of this in the stem which gives to all the grasses so much firmness. On the other hand, the pea will reject this, and will take up whatever calcareous substances (those formed of lime and its compounds) the water of the soil contains, these being rejected by the wheat plant. But we are encroaching upon the subject of plant food, which may be presented at some future time.

PRACTICAL REMARKS.

The roots of plants are liable to diseases, the principal one being root-blight, or, as it is popularly known among horticulturists, rotten-root. This disease is caused by an excess of moisture in the subsoil, or by a large accumulation of stagnant water. Carrying this off by thorough under-draining will secure health and a vigorous root growth. We have seen varieties of sweet apples, such as the Talman and Ladies' Sweet, badly affected by rotten-root, not at the extremities of the rootlets, but just at the junction of the roots with the collar of the tree. The only remedy in the way of cure is to prevent, by top-working two feet above the surface of the ground.

Roots have insect enemies also. The destructive influence of the dreaded phylloxera has been seriously felt in the wine-growing countries of Europe. The apple-root louse, or woolly aphis, has also done much injury to the orchards of southern Illinois. Some hold the theory that rotten-root is caused by this insect, but we think it is erroneous, from the fact that all the roots which we have examined show no trace of the presence of the aphides, which always leave knotty excrescences upon the roots as the result of their depredations.

Root-pruning has been universally practiced throughout Great Britain for the last sixty years, to produce fruitfulness in barren trees, and as a preventive of pear-blight-the theory being held that if the exuberant growth of some varieties can be checked, and the trees compelled to finish their annual growth and ripen their wood-buds early in autumn, no blight will ensue. Does the root of the stock affect the cion? is an inquiry which has always agitated horticultural circles. We do not believe it does; but we do believe, and know from ocular demonstration, that the cion wonderfully affects the roots of the stock. Take a strong one-year-old apple seedling, and divide it into four sections; graft one section with a cion of Soulard Crab (a variety of Pyrus coronaria), the second with Ben Davis, the third with Jonathan, and the fourth with Yellow Bellflower, and note the result. The roots of the stock grafted with the crab, when a year old, will be black, scrawny, and few in number, and all semblance to the roots of an apple tree will be gone, while the three other varieties of apple will have numerous healthy roots of a light yellow, or brown orange color, according to variety. Observant nurserymen, who handle large quantities of young stock, can readily distinguish the popular varieties of apples by simply looking at the roots of each; the