When the Lebanese-American philosopher, poet, and artist Etel Adnan died last November, at 96, the art world mourned. In New York, her distilled yet vibrant landscapes are up at the Guggenheim, enjoying a retrospective that closes on January 10. Adnan used simple shapes to create images that float buoyantly between landscape and abstraction. Though she often applied her oils on canvas with a knife, resulting in crisp, bright lines, the works in Galerie LeLong’s “Discovery of the Immediate” were made with a paintbrush and use very little color to capture flowers, fruits, inkwells, and flasks. These paintings are part of Adnan’s last series. —E.C.