tracery, bands or bars of stone, wood, or other material, either subdividing an opening or standing in relief against a wall and forming an ornamental pattern of solid members and open spaces. The term refers especially to the subdivisions in the arched openings of Gothic architecture. In Romanesque design the enclosing of twin openings within a single arch created a wall space above them, where a circular or quatrefoil opening was pierced as an ornament. This plate tracery became more complex in 12th-century rose windows of the Cathedral of Chartres and in early Gothic English churches. Later, windows became larger, areas of solid stone smaller, and masonry members more slender; the patterns in the spaces above the arches were created by bars of stone rather than by a pierced design. Such bar tracery (e.g., in the cathedral at Reims) prevailed in both France and England by the first half of the 13th cent., creating circles, trefoils, quatrefoils, and other varied geometrical designs. The terminations of these shapes, termed cusps, were finished in square or sharp points or in ornamental blobs. Tracery came gradually to be used also for ornamenting buttresses, gables, spires, interior walls, and choir screens. In France, Rayonnant-style tracery was marked by a multiplication of thin vertical bars within a rational, geometrical order. In England there appeared in the mid-13th cent., mainly in window heads, a new curvilinear tracery of free, flowing curves. The French developed that type into the elaborate, flamboyant tracery of the 15th cent., which produced windows and architectural adornment of amazing lightness and intricacy, as in the cathedral at Rouen and in the wood choir stalls of Amiens. In England, however, the flowing forms were abandoned c.1375, and emphasis passed to perpendicular mullions running the entire height of the windows. By the early part of the 16th cent. the severe tracery of the Perpendicular style, with its closely spaced verticals, was dominant in both windows and wall adornment, providing a contrast to the elaborate fan vaulting, as in the Henry VII Chapel in Westminster and King's College Chapel, Cambridge. Medieval tracery achieved extraordinary effect in the great French rose windows of stained glass.