Though the subject we have placed at the head of this communication, has received some attention from scientific cultivators in certain parts of the country, and allusions to its use and importance have been made in "the Horticulturist," whose different volumes form our best standard book of reference, yet it must be confessed that a thorough treatise upon the subject is a very great desideratum, especially in this land of clear skies, arid atmosphere, burning suns, and summer drouths.

There are certain departments of horticulture, and certain processes and operations of the gardener's noble and beautiful art, that either have been overlooked and neglected in this country, or that have not yet had their time and opportunity for development. One is the "Hybernation of Plants;" another "the Proper Feeding of Trees;" another "the Value, Beauty and Cultivation of Evergreens;" and last but not least, "the Benefit of Mulching," to trees, plants, seeds, etc. In some future communication, Mr. Editor, I purpose to give you the results of my observation, experience and reflection upon the former themes, should you allow me, while I confine my remarks, for the present, to the subject of "mulching." In England and on the continent of Europe, this matter is receiving something of the attention it deserves, and yet, if the process has its value on the sea-girt isle of mists and fogs, where old Sol himself shines hardly brighter than our harvest moon, of what vastly greater importance must it be in this climate, where annual and long continued drouths seem a part of the order of nature, and where the hygrometer indicates a greater deficiency of moisture than is known in any European atmosphere.

Indeed, I regard mulching as our prime and especial necessity. - the must indispensible thing in North American Horticulture. For in the first place, the operation of mulching. - or covering over the surface of the ground - prevents the evaporation of the moisture that is so requisite to the rooting of new plantations, to the development of luxuriant foliage, and the production of perfect flowers, and fair, juicy large sized fruits. Again: the operation of mulching not only prevents, to a great extent, the escape of moisture, but also, and what is of greater importance, the passing away from the earth of the volatile gases that are held in solution in the water, and which, sucked in by the minute mouths of the radicles or spongioles, give nourishment to the plant or tree.

That mulching is of great value in the case of young and newly planted trees, by preventing the process of evaporation, is universally admitted in theory, and to a certain extent carried out into practice; and yet, but few seem to be aware of its value in retaining the nourishment as well as the moisture in the earth, and thus, by both these means, contributing to the luxuriant and heathful condition of plants and trees already rooted, and well established in the soil. But observation, however, as well as actual experience, has fully convinced me, that trees will not only put forth more luxuriantly, and grow more vigorously, but that the fruit will be far larger, fairer, and juicer, for mulching during the hot season. And I hazard the observation, that in the culture of pears, and certain kinds of apples. - such as the Roxbury russet, that are generally small and knerly on a gravelly bottom, careful mulching is almost equal to a clay subsoil.

And here let me say, by way of parenthesis, that in the cultivation of these fruits, it is not, I think, any nutritive element in the clay soil, but only its power of retaining moisture, that gives it the advantage over a gravelly substratum. By carefully mulching, however, I do not mean a wisp of straw, hay, weeds, or small brush, nor a shovel of spent tan, hub-chips or saw-dust, placed just round the trunk of the tree, but a covering of the ground, if possible, as far as the roots extend. There are some absurd people, who seem to think, if we are to judge them by their practice, that somewhere at the butt of the tree is a great mouth, in which the tree takes in its food and drink; and, accordingly, they put all the nourishment, whether liquid or solid, "right round" the trunk. Whereas the truth is, the numerous little mouths that drink in the moisture, and the nutritious elements that are disolved in it, are in the little spongioles that form the very terminations of the radical branches; and our course of treatment should be based upon this fact, in watering, manuring, and mulching.

Mulching then, in the first place, prevents, in light gravelly soils - and in dry seasons in all soils - the evaporation of the moisture necessary to that flow of sap, that shall make a luxuriant growth, fine foliage and fair, large juicy fruit.

And secondly, as the elements that nourish the tree are contained in the moisture in solution, and a dry state of the earth must thus cut off the supply of food, mulching actually nourishes the tree. In proof of this, I might, would my space allow, adduce numerous facts; but experiments are so easily tried, that such evidence is hardly necessary here.

In conclusion, as the season for planting flowers, roots, seeds, etc, is at hand, I must say one word in favor of mulching for them.