(δις, "twice," and ἀδελφός, "a brother"), the 17th clas in the sexual system, comprehending those plants which bear hermaphrodite flowers with two sets of united stamina; but this circumstance must not be absolutely depended on. They are the papilionacei of Tournefort, the irregularis tetrapetalii of Rivinus, and the leguminose of Ray. See BOTANY Index.

DIadem, in antiquity, a head-band or fillet, worn by kings as a badge of their royalty. It was made of silk, thread, or wool, and tied round the temples and forehead, the ends being tied behind, and let fall on the neck. It was usually white and quite plain; though sometimes embroidered with gold, and set with pearls and precious stones. In latter times, it came to be twitted round crowns, laurels, &c. and even appears to have been worn on divers parts of the body. See CROWN. The word comes from the Latin diademum; of the Greek διάδημα, "a little band encompassing the head," of the verb διάδεω, cingo, "I gird."

DIadem, in Heraldry, is applied to certain circles or rims serving to inclose the crowns of sovereign princes, and to bear the globe and cross, or the fleur de lis, for their crest. The crowns of sovereigns are bound, some with a greater and some with a less number of diadems.—The bandage about the heads of Moors on shields is also called diadem in blazoning.

DIARESIS, in Surgery, an operation serving to divide and separate the part when the continuity is a hinderance of the cure.

DIARESIS, in Medicine, is the confining of the vessels of an animal body, when, from some corroding cause, certain passages are made which naturally ought not DIA

Diæresis to have been; or certain natural passages are dilated beyond their ordinary dimensions, so that the humours which ought to have been contained in the vessels extravatate or run out.

DIÆRESIS, in Grammar, the division of one syllable into two, which is usually noted by two points over a letter, as aulai, instead of aulae, diffolienda for diffollienda.

DIÆTETÆ, in Grecian antiquity, a kind of judges, of which there were two sorts, the cleroti and diallacterii. The former were public arbitrators, chosen by lot to determine all causes exceeding ten drachms, within their own tribe, and from their sentence an appeal lay to the superior courts.

The diallacterii, on the contrary, were private arbitrators, from whose sentence there lay no appeal, and accordingly they always took an oath to administer justice without partiality.