BOLETUS, an extensive genus of Fungi, consisting, according to the old botanists, of leathery masses, which are sometimes of consider able thickness, and having the spores lodged in tubes which occupy the same situation as the plates in the gills (or hymenium) of the common mushroom. Fries, the great modern describer of Fungi, defines the genus thus :—Ilymenium formed of a peculiar substance, altogether distinct from the cap, entirely composed of tubes united into a porous layer ; these tubes are undivided, separable from each other, long, cylindrical, or angular, open from end to end, and bear asci (spore-cases) on their inside; asci cylindrical, with small roundish spores; the stalk is central, and often netted; the cap is fleshy, soft, spread out into a hemispherical form ; veil present in many of them. Ile includes within his definition but a small number of the old Bo/di, referring the principal part to Polyporus, which is especially charac terised by having the tubes of its hymenium inseparable from the cap, which is more leathery, and usually without a stalk.
The true Boleti are generally found growing on the ground in woods and meadows, especially in pine woods : the l'olypori are commonly met with on'treen, especially pollards. Of the former, several species are eatable, as 11. edulis, B. umber, B. subtomentosus, and B. granulates; others are acrid and dangerous. Of these Dr. Badham, who has written on the Esculent Funguses of England, recommends only B. edulis and B. scuber.
B. edulis, the Edible Boletus, has the following characters or cap from six to seven inches across, smooth, with a thick margin varying in colour from light brown or bronze to bay, dark brown, or black, or a mixture of all these colours; the epidermis firmly adhe rent to the flesh, which is fine, and except the part in immediate contact with the skin, white ; the under surface of the cap nearly flat, often presenting a circular pit or depression round the stalk ; the tubes at first white, then yellow, lastly of an olive or yellow green tint, in the earlier stage of their growth closed ; afterwards as the cap expands stopped up with a waxydooking material of a dirty pearl colour ; stem varying much in shape at different periods of the growth of the'Boletus, always thick And solid, at first white but moon changing to fawn-colour, beautifully netted with reticulations. As the period of the ripening of the spores advances the under part of the cap swells, the waxy matter is absorbed, the tubes present deep and rounded orifices to the eye; and emit an ochreous green dust, which consists of sporulea. After this the whole fungus becomes flaccid,
the tubes turn to a dirty green, and decomposition rapidly proceeds.
This &Aetna grows in woods consisting of pines, oak; or chestnuts; it is most abundant in autumn, but occurs in spriog and summer. Dr. Badham says of other Fungi likely to be comfounded with it :— " The B. castuneus, which bears some little resemblance to it, ie at once distinguished by having a cottony fibrillose stem without reticulation; a downy cap, and dirty yellow dust : neither can it be confounded with the B. subtomentosus or B. /urfdas, because in addition to many other points of difference, both these change colour on being cut or bruised." As an article of diet, Dr. Badham says " It imparts a relish aliko to the homely hash and the dainty ragout, and may be truly said to improve every dish of which it is a constituent." B. 'caber has a cap from three to seven inches across the surface, which becomes viscid when moist and is invariably downy. There are two varieties, in one of which the pilaus is of a beautiful deep orange hue and the stein black. In the other the pileux is gray and the stem covered with orange scales. The flesh is thick and flabby, of a dingy white, not greatly changeable In young specimen; but deepening in colour when old. It is not so agreeable as the last species.
B. officinalia, supposed to have been the 'Ayapisbr of Dioscorides, is an old-fashioned medicine remarkable for the extreme acridity of its `powder; it acts as a powerful purgative, but is never employed at the present day.
B. igniarius, when dried and sliced, furnishes the German Tinder, or Amadou, a leathery substance sold in the tobacconists' shops. [Asasnon.] B. destructor is one of the many species of Fungi the ravages of which are too well known under the name of Dry Rot. Their destruc tive qualities are not however caused by the fructification, or the part which we commonly consider the fungus itself, but by the ramifica tions through the substance of the wood of what botanists call the Thallus and gardeners the Spawn of such plants, which is in effect their stem and root in a mixed state. Other species of Fungi produco dry rot. [M ear Lies.]