Goings On About Town: Shapeshifters

After a decade in which abstraction was all about gesture and flatness, two shows in the nineteen-sixties-- Lawrence Alloway's "The Shaped Canvas" and Frank Stella's "Shape and Structure" proposed that the support of a painting mattered as much as the paint that went on it. One of Stella's irregular polygons, a yellow triangle impinging on a red square via a zigzag of turquoise, anchors this impressive selection of art by rectangle rejecters, from the stalwarts Robert Mangold and David Novros to the younger Ruth Root and Joe Bradley. The show's knockout is Elizabeth Murray's "Sentimental Education," from 1982, which conjoins three canvases: one jagged, one coiled, and one shaped like a bulbous apostrophe.