DRUPA, in botany, a species of seed vessel, that is succulent, has no valve or ' external opening like the capsule and pod, and contains within its substance a stone or nut. The cherry, plumb, peach, apricot, and all stone fruit, are of this kind. The stone, or nut, which, in this species of fruit, is surrounded by the soft pulpy flesh, is a kind of woody cup, containing a single kernel or seed. The definition just given will apply to every seed-vessel denominated drupa in the " genera plantarum." The mond is a drupa, so is the seed-vessel of the elm tree and the genus rumphia ; though far from being pulpy or succulent, the first and third are of a substance like leather ; the second like parchment. The same may be said of the walnut, pistacia-nut, and some others. Again, the seeds of the elm, flagellaria, and the mango-tree, are not contained in a stone. The seed-ves sel of burr-reed is dry, shaped like a top, and Contains two angular stones. This species of fruit, or more properly seed vessel, is commonly roundish, and when seated below the calyx, or receptacle of the flower is furnished, like the apple, at the end opposite to the foot-stalk, with a small umbilicus or cavity, produced by the swelling of the fruit before the falling of the flower-cup.
• DRY rot, a disease incident to timber used for building, such as flooring hoards, joists, wainscotting, &c. Dr. Darwin is of opinion, that the dry rot may be entirely prevented by soaking the timber first in lime water till it has absorbed as much of it as possible, and after it has become dry, immersing it in a weak solution of vitriolic acid in water, which he supposes will not only preserve it from decay for many centuries (if it be kept dry,) but also render it less inflammable ; a circum stance that merits considerable attention in constructing houses. In the transactions of the Society for the Encouragement of Arts, we meet with the following account of the cause of the dry rot in timber, and the method of preventing it, communicat ed by Mr. Batson, of Li mehouse. He ob serves, that the dry rot having taken place in one of his parlours, to such a de gree as to require the pulling down part of the wainscot every third year, and per ceiving that it arose from a damp, stag nated air, and from the moisture of the earth, he determined, in the month of June, 1783, to build a narrow closet next the wall through which the moisture came to the parlour. This expedient had the desired effect. But, though the rot
its the parlour was totally stopped, the evil soon appeared in the closet, where fungi of a yellow colour arose in various parts. In the autumn of the year 1786 the closet was locked up about ten weeks : on opening it, numerous excrescences were observed about the lower part ; a white mould was spread by a plant re sembling a vine, or sea-weed ; and the whole of the inside, china, &c. was cover ed with a fine powder, of the colour of brick-dust. On cleaning out the closet, it was discovered that the disease had affected the .wood so far as to extend through every shelf, and the brackets that supported them. In the beginning of the year 1780, he determined to strip the whole closet of lining and floor, not to leave a particle of the wood behind, and also to dig and take away, about two feet of the earth in depth, and leave the walls to dry, so as to destroy the roots or seeds of the evil. When, by time, the admis sion of air, and good brushing, it had be come properly dry and cleansed, he filled it, of sufficient height for the joists, with anchor-smith's ashes, because no vegetal.
Me will grow in them. The joists being sawed off to their proper lengths, and ful ly prepared, they and their plates were well charred, and laid upon the ashes ; particular directions being given, that no scantling or board might be cut or planed in the place, lest any dust or shavings might drop among the ashes. The flooring-boards being very dry, he caused them to be laid close, to prevent the dust getting down, which, perhaps, in the course of time, might bring on vegeta tion. The framing of the closet was then fixed up, having all the lower pannels let in, to be fastened with buttons only, so that, if any vegetation should arise, the pannels might with ease be taken out and examined. In some situations, it might be expedient and necessary to take out a greater depth of earth ; and where ashes can be had from a foundry, they may be substituted for those of anchor smiths ; but house ashes are by no means to be depended upon. At the expiration of seven years from the period of making this experiment the wainscot was remov ed, and the flooring-boards also taken up, when they were found entirely free from any appearance of the rot : two pieces of wood (yellow fir) which had been driven into the wall as plugs, without being pre viously charred, were alone affected with this disease.