A visitor to “The Belgian Marbles,” the recent exhibition by the Reena Spaulings collective, would have noticed two things right away. First, thanks to a series of colorful lithographs of the shadows of palm trees called “A Place in the Sun (Shadows)” (all works 2009), marble surfboards (Mollusk [Portoro] and Mollusk [Rosa Portogallo]) installed on the balcony, and brightly colored yoga mats on the floor, the exhibition felt tropical—but for no apparent reason: This being Brussels, the effect was incongruous, or merely weird. Second, everything seemed completely offhand, as if the artists had