That all plants in their growth need sustenance, and receive it from some source, is known and acknowledged by all; but how it is obtained, from whence, and how taken into their constitution, is not so plainly seen or generally understood. To offer any new ideas on this question I do not lay the least claim; my object therefore will only be to place before the reader some plain, simple, and easily understood observations on the composition of all vegetable substances, the source from which these substances are derived, and how they arc taken into the organization of plants.

Vegetable, and all other substances that present themselves to our view, are divided, or may be resolved, into combustible and incombustible—organic and inorganic—matter. Organic matter consists of that in which life has at some thus existed; inorganic, on the contrary, of dead matter. All plants will therefore come under the head of organized matter, as being the seat of life. All organized matter is capable of being resolved into simple or elementary substances; thus all organized vegetable matter is composed of no more than four elements that it is necessary for us to examine in our present article—viz., carbon (known to us as charcoal or the diamond), oxygen, hydrogen, and nitrogen. With the exception of carbon, these elementary bodies are known to us only in the form of gases. The properties and relations which each of these elements bears to vegetable life are important, and might with profit be but suffice it for the present to say that each one performs Its appropriate function in the economy of nature. moms three of these four elements an gases, yet much of the solid parts of plants is made up of them. When alone, at the ordinary temperature of the air at the surface of the earth, they form invisible kind. of air; when united in the different proportions in which they combine, they form woody fibre, starch, gum, and sugar, which, united, constitute the various vegetable forms which it is the aim of all agriculturist. to raise with certainty, rapidity, and abundance. Of these elements, all plants are made up of by far the greatest proportion of carbon, the amount approaching one-half, the three others going to mike up the other half. The oxygen amount. to about one-third, hydrogen to about five per cent., and the nitrogen rarely to more than 2  1/2 per cent. of the dried weight of plants: In their green state, of course the proportions would be different. As before stated, carbon is the only element of plants that appears to us in any other form than the gaseous; but it must be evident to all that plants cannot appropriate into their composition any solid substance, and that therefore the carbon must be absorbed in a different form or state Not that in which we can see it with our eyes, or feel it with oar fingers. When we burn charcoal or the diamond, which are the pate forms of carbon in nature, in the open air, they pan Of, with the exception of a small residue, into the air, in the form of carbonic add gas; in this state carbon is capable of being dissolved in water, and also of being absorbed by the plant.

Having shown that all plants an composed of the four elements, carbon, oxygen, hydrogen, and nitrogen principally, which, when united, form woody fibre, starch, gum, and sugars, which go to make up the composition of plants, we next need to show the source from which they are derived. All animal as well as vegetable substances are made up of the elements above named, and the soil of the earth's surface is composed in part of decayed and decaying animal and vegetable substances. The air is composed principally of a mixture of oxygen and nitrogen, with a very small per-centage of carbonic acid gas, and also is capable of being imbued with a quantity of water in a fine vapour state. Water is composed oxygen and hydrogen, and is capable of absorbing all other gases, and of imparting them to other substances. All plants are first fixed in the soil by their roots, and rise into the air, producing their stems and leaves above the surface in the atmosphere. Necessarily, then, all plants must derive their sustenance through one or both of these mediums. Water absorbs ammonia and other gases which furnish nutrition for plants; the water descends to the soil in the form of rain, or as dew is condensed at the surface, carrying along with it the gases absorbed, imparting them to the soil, which in turn imparts them to the growing plant through its roots, either in a fluid or gaseous state; the roots prepare and transmit them to the steal, where some of the elements needed for the growth are absorbed and elaborated; the leaves also performing an important part in absorbing from the atmosphere certain gases and emitting others, acting as the breathing organs of the plant. It will then be seen that plants derive their sustenance from both the soil and atmosphere, and take into their construction, through their roots and leaves, all their nutriment. Both the soil and the atmosphere are essential to the growth of the plant, for either alone will not support vegetable life for any length of time. The soil must be stored with plant food, such as decayed animal or vegetable substances, that the combined action of the soil, water, and air may render capable of being taken into the system of the plant; unless so stored, the plant will languish and finally die. It is the same with plant as with animal life; if either is deprived of food, a languishing conditions is induced, while if it is abundantly supplied, they both thrive sad grow from similar seasons.

The increase of a plant in size is supplied principally from the nutrition obtained through the medium of the soil; all its mineral elements are derived therefrom, as well as a large share of its combustible elements. If the soil is incapable of furnishing theta in order to grow plants, we must add to the soil such materials as will supply the nutrition from elements. A virgin soil possesses a quantity of nutrition from vegetable substances that have decayed on it a surface in the course of time, and hence all such land is proverbial for its good crops; but after being cropped awhile it becomes exhausted, and then a supply from some other source becomes necessary, just as your own supply of provisions needs replenishing after exhaustion. These are plain, common-sense reasons, comprehended by the simplest. But the question arises in the minds of some, How does the manure act in the soil? I might answer by explain its chemical operation, but it would be a better understood reason to answer, that it acts precisely on the same principle as does the corn in the crib fed to our fattening stock, or the provision in the store-house for our own consumption. If we provide no or fodder for our cattle, or have only a scant supply, and that of poor quality, we cannot expect our cattle to thrive, and neither need we expect that large crops of grass, grain, or vegetables can be produced without supplying manure to the soil from which the plants may derive food. The soil consists of a mixture or combination of a variety of substances, some of which are essential to the growth of one kind of plant, and others to a different kind, and others are rejected as non-essential if not poisonous; and here we see the Wisdom that directs all things, and the impossibility of our comprehending said explaining, by human reasons, certain immutable laws of nature. We place a promiscuous variety of articles of food before man, and he will select certain kinds as con. genial to his nature, and reject others as injurious; this we call reason in man; the same large variety, placed before the horse or ox would result in the selection of a larger and different variety, while many are still rejected as uncongenial; this, in the brute creation, we term instinct; but what shall we term the seine election in the vegetable kingdom ? Watch the horse as he pulls his feed of hay through the rack, mixed with various kinds of plants, congenial or otherwise, to his nature; ice him reject all that is uncongenial by the action of the lips. The same election is made, and, in a similar way, by the roots of the plant, which act in the same capacity to the plant that the lips and mouth do to the horse. There appear to be certain immutable laws which govern the growth of plants, that are far from being generally understood; why, for instance, in the growth of different kinds, one requires the presence in the soil of certain elements or compounds, while another kind demands an entirely different constitution of soil in order to a successful growth. For the present I defer the solution of these problems to older and wiser heads.—W. H. WHITE, in Country Gentleman.