DRY ROT is a disease affecting timber, pro duced by the attacks of fungi. The first sign of it consists in the appearance of small white points, from which a filamentous substance radiates parallel with the surface of the timber. This is the first stage of growth of the spores of the fungus, and the filamentous matter is their thallus or spawn. As the thallus gathers streugth, it insinuates its filaments into any crevice of the wood, and they, being of excessive fineness, readily pass down and between the tubes from which the wood is organized, forcing them asunder, and completely destroying the cohesion of the tissue. When the thalli of many fungi interlace, the radiating appearance can no longer be remarked ; but a thick, tough, leathery white stratum is formed wherever there is room for us development, and from this a fresh supply of the destructive filamentous thallus is emitted with such constantly increashig rapidity and force, that the total ruin of timber speedily ensues where circumstances are favourable for tho growth of tho fungi. Dry rot consists of the thallua of Merulius lacrymans, or Polyporus destructor, two highly organized fungi ; but any of the fungi that ere commonly found upon decaying trees in woods are capable of producing dry rot, and the most rapidly-spreading and dangerous kinds is caused by the ravages of different species of Sporotrichum. The latter throw up from their thallus whole forests of microscopic branches loaded with repro ductive spores, of such excessive smallness that they may insinuate themselves into the most minute crevices or flaws even in the sides of the tubes of which timber consists, and they are in finitely more dangerous than merulii or polypori, which seldom fructify. The circumstances that are most favourable to the development of the dry rot fungi aro dainp, unventilated situations, and subacid state of the wood. The latter condition, especially in oak, is easily produced by a slight fermentation of the sap which remains in the timber, especially if the latter has not been well seasoned before being employed. It has been proved experimentally that fluids which, in their ordinary state, will not produce fungi, generate them abundantly if ever so slightly acidulated. Dutrocliet found that distilled water, helding solution a small quantity of the white of egg, will not generate fungi in a twelvemonth ; but upon the addition of the minutest quantity of nitric, sulphuric, muriatic, phosphoric, oxalic, or acetic acid, it generated them in eight days' time in abundance. Alkalescent infusions possess the same property. The only poisons which will prevent the appearance of fungi aro the oxides or salts of mercury. A solution of fish-glue yields fungi rapidly and in great abundance ; but a small quantity of red precipitate or corrosive sublimate destroys this power entirely. It is, moreover, an important fact that no other mineral preparation lut.s any such properties. Dutroehet ascertained that other metallic oxides acted differ ently. Oxides of letul and tin hastened the develop
ment of fungi ; thorns of iron, antimony, and zinc Were inert ; and oxides of copper, nickel, and cobalt, although they retarded the appearance of fungi, yet did not prevent their growth in the end. These facts are confirmed by the experience of the use of Kyan's process for preparing tiinber, which consists in submitting the wood to the action of corrosive sublimate. Inunersiog the wood in chloride of zinc likewise prevents the attacks of fungi, and also submitting it to the action of the vapour of creosote. Dry rot also occurs in animala. Specimens of hymenopterous insects resembling wasps have been bronght froin the West Indies, with a fungus allied to Splicer's militaris growing from between their antenor come, and it is positively asserted by travellers that the insects fly about while burdened with the plant. Upon opening the bodies of the wasps, they are found filled with tho thallus of the fungus un to the orbits of the eyes and the points of the tarsi, the whole of the intestines being obliterated. In such cases it is to bo supposed that the thallus of the spliceria first kills the wail) by compressing and drying up the body, and then, continuing to grow, occupied tho whole of the cavity of the shell of the insect. A more common Waimea of animal dry rot is the &tease in silk-worms called la Muscadine. Silk-worms of all ages are occaskmally liable to become sickly and to die, soon after death beconiing stiff, and acquiring such a degree of firmness as to be readily broken. They then throw out from their surface a sort of white efflorescence, which is the fructification of the fungus called 13otrytis bassiana, their inside being filled by the thallus of tho same pLant. If some healthy caterpillars are placed beneath a bell-glaas, along with a small portion of worm killed by the botrytis, they soon catch the disease, exhibit the same symptoms as those already mentioned, and eventually perish, having no doubt been infected either by rubbing tlaemselvui against the dead worm, or, which is more probable, haviug received upon their skins the infinitely minute seeds dis persed by tho botrytis. If healthy crysalids are inoculated by the introduction below their shell of a little of the botrytis matter upon the point of a needle, they also [sicken and die. In these cases effects aro produced upon insects similar to those upon timber ; that is to say, vitality in the one ease, and cohesion in the other, is destroyed by the growth of the thallus of certain fungi, which spread with great and irresistible rapidity, and fructify where occasion offers. Boletus destructor is also one of the dry rot fungi.—Eng. Cyc.; Toad.
DSO and Dso-mo. TIBETAN. The bull and cow, produce of the male yak and common cow.
DUA, Attau. Supplication, prayer. Dua-i Masura, supplication for the remission of sins. Dua-i-Qunut, a prayer of praiae.