Amongst the many valuable communications in the Horticulturist, this esculent has not received the attention which it deserves. Many persons suppose that there is great difficulty in its artificial production, almost amounting to a mysterious secret known only to a few.

The poisonous properties of many varieties of fungi, and the difficulty of distinguishing the good from bad, also militates against them, and renders it necessary to be cautions in making them an article of food. Nevertheless, mushrooms are very generally esteemed when properly cooked, and are nutritious when used in moderation. Chemically, they have more resemblance to flesh than any other vegetable. In some parts of Russia, it is said the peasantry depend on mushrooms and bread for the greater part of their sustenance. They employ about fifty kinds of fungi as food. In Rome there is an "Inspector of Funguses," who attends the markets as a guarantee for public safety, and strange to say, our common edible mushroom, (Agaricus campestris,) is interdicted; any specimens of it brought to the fungus market, are sent under escort and thrown into the Tiber.

It appears from the remarks of mycologists, that the majority of funguses are harmless; the poisonous varieties being the exception, the innoxious and esculent the rule. But the difficulty lies in the selection, as we have no definite guide to point out what sorts are, or what are not poisonous; even some of the wholesome kinds acquire noxious properties, when grown under peculiar circumstances. Soaking in vinegar destroys much of the poisonous qualities if present. Heat also extracts the deleterious properties from many that would be unsafe to eat in a raw state. Various tests have been recommended. The presence of a free acid has been considered a sign of harmlessness. This is found not to be conclusive, as many, good and bad, will redden litmus paper. Cooking them with a silver spoon, under the impression that if bad the spoon will change its color, is also an erroneous idea. Cooking an onion with them is said to be a good test; if they are edible the onion will maintain its original color, while it will turn black if the mushroom is poisonous.

Selecting by color has also its advantages; many of the most noxious species are of a snowy whiteness, while others of a less tempting color are perfectly harmless, so (hat great care and experience are requisite to discriminate those that can be eaten with safety.

The Agaric campestris, or common mushroom, is the only species that is generally grown artificially. It is thus botanically described: Stipes, (or stalk,) two or three inches in length, white, solid, fleshy, furnished with an annular veil, (a thin membraneous substance encircling the stalk.) Pileus, (cap or edible part,) fleshy, dry, convex, at length plane, white, changing from yellowish to brownish. Gills, (thin parallel plates underside of the cap,) free, ventricose, (swelling unequally on one side,) pink, changing to deep purplish brown. Flesh, (internal substance,) white.

There are several species of the Agaric besides the above, and also a few varieties of the A. campestris that are sometimes grown for using in a recent state. It is unnecessary to describe them here, as those who purchase spawn need be under no apprehension of receiving a spurious article; at least so far as my experience goes, I have never seen disappointment in this respect. So far from there being any difficulty in growing them, I venture to say that not one in fifty who makes the attempt will fail. Of course, some little attention is requisite, as with everything else artificially circumstanced. A knowledge of the condition under which they are most plentifully found in nature, will be of material assistance to the grower. The germs of fungi seem to be widely diffused in the atmosphere; all that is wanting for their development being a favorable medium. In very dry seasons, mushrooms are most plentiful in low situations, on strongish soils; on the contrary, should there be much wet, they are more abundant in upland and drier localities. A continuance of warm, dry weather, followed by slight showers, and a hazy, still atmosphere, brings them most profusely. These considerations are worthy of keeping in mind in their artificial culture.

There is no particular season for making a mushroom bed. In winter it requires to be under cover, and in summer the difficulty lies in keeping it cool and moist. Autumn is perhaps the best season for building a bed out of doors, and if a constant supply be an object, a bed should be made up in some spare cellar about the beginning of November.

Before entering into the details of management it may be useful to make a few remarks upon the propagation of spawn. Summer is the best time for performing this operation. Procure some horse droppings; if there is a sprinkling of short litter with them, so much the better; cow dung and light loamy soil, or road scrapings, in about equal proportions; it is not particularly necessary that they shpuld be in exact quantities. I mention this in passing, as an idea sometimes gets abroad, that unless everything is mathematically adjusted by number or weight, it would be folly to expect a satisfactory result. Mash these ingredients together with water, into a thick mortar, and spread it out three inches in thickness, in an open shed to dry. As soon as firm enough, cut it with a spade in squares of seven or eight inches, set them on edge, and turn them occasionally to facilitate their drying. When they will admit of being handled with safety, cut with a knife two or three holes, about two inches in diameter, little more than half through the brick, and fill each hole with good spawn, plastering it over with a portion of what was cut out. They should now be left until quite dry. Have ready a quantity of fermenting manure which has been well sweetened by frequent turnings.

Spread a layer of this six or eight inches in thickness, and build the bricks on it with the spawned side uppermost, drawing the pile up to a point, then cover the whole with the warm manures. A genial warmth of about sixty degrees will be sufficient to cause the spawn to run through the whole of the bricks; when this takes place the process is ended. They can be laid past in a dry tossing it into a heap to ferment. Upon its coming into a good heat, turn it over, bringing the rougher portions into the center; this should be repeated until it is well mixed and equally rotted. The object is to bring the whole into an equal state of fermentation without rottenness; to drive off excessive moisture and subdue the burning heat, with least possible loss of the essential gases. If a third part of old hot-bed manure is mixed with it, it will moderate the heat, and give the bed a consistency that it would not otherwise possess. Having it in readiness, choose a spot for making the bed; if under the shade of a tree so much the better. Mark out the ground four or five feet wide, and length to correspond with the quantity of manure. Commence by throwing in a layer of the least decayed portions of the dung; then build the whole up in a rounded ridge three feet high.