Sept. 30 to Dec. 31 at the National Gallery of Art Do well-established museums get turf-conscious? Or green with envy? I wonder what the National Portrait Gallery thinks of the National Gallery of Art mounting “The Serial Portrait: Photography and Identity in the Last One Hundred Years.” The exhibit will include roughly 150 works that demonstrate how photographers have approached documenting individuals, including themselves, over the course of days, months or years, showing the passage of time. Featured photographers include Alfred Stieglitz, Paul Strand, Harry Callahan, Andre Kertesz, Lee Friedlander, Emmet Gowin, Nan Goldin, and Nikki Lee. All well and good, but it is a bit of a shot across the bow. Curators: weapons at dawn in John Marshall Park?