Next to the common mushroom, in regard to the success attending its cultivation, comes that of the _Pietra funghaia_, a plant unknown to Clusius, but described by Mathiolus and Imperato, under the name of the ‘stony fungus.’ Cesalpinus has added to their accounts, directions for procuring it the whole year through, which, he says, is to be done either by irrigating the soil over the site of the stone, or by transferring the _Pietra funghaia_ with a portion of the original mould, and watering it in our own garden. Porta adds, that the funguses take seven days to come to perfection, and may be gathered from the naked block (where this has been properly moistened) six times a year; but in preference to merely watering the blocks, he recommends that a light covering of garden mould should be first thrown over them. The _Pietra funghaia_, though its range of territory be extremely small, lies embedded in a variety of soils, in consequence of which its Polyporus, like our own mushroom, is very various in flavour, depending on the kind of _humus_ in which its matrix happens to be placed. Those that grow on the high grounds above Sorrento, and on the sides of Vesuvius, are in less esteem than such as are brought into the Naples market from the mountains of Apulia.[98] A third fungus, which we have the means of producing _ad libitum_, is that which sprouts from the pollard head of the black poplar;[99] these heads it is usual to remove at the latter end of autumn, as soon as the vintage is over, and their marriage with the vine is annulled; hundreds of such heads are then cut and transported to different parts; they are abundantly watered during the first month, and in a short time produce that truly delicious fungus, _Agaricus caudicinus_, the _Pioppini_, which, during the autumn of the year, make the greatest show in many of the Italian market-places. These pollard blocks continue to bear, for from twelve to fourteen years; I saw a row of them in the botanic garden at Naples, which, after this period, were still productive, though less frequently, and of fewer Agarics at a crop. The practice of rearing funguses from the poplar is not modern; Dioscorides knew, for he tells us that if we “bark the white or black poplar, cutting the bark into pieces and covering it with horse-dung, an excellent kind of fungus will spring up, and continue to bear throughout the year:” by way of comment to which passage Mathiolus adds, that a little leaven[100] will produce an abundant crop in four days. Another fungus, which I have myself reared (_Polyporus avellanus_), is to be procured by singeing over a handful of straw a block of the cob-nut tree, which is then to be watered and put by. In about a month the funguses make their appearance, which are quite white, of from two to three inches in diameter, and excellent to eat; while their profusion is sometimes so great, as entirely to hide the wood from which they spring.[101] Dr. Thore says, that in the