As purposefully noted here, the latest enticing show at Washington's National Gallery of Art is a gem - not only because of its play on words and the fine representation on museum walls of a dying tradition. Recall the playful slogan of yesterday, "What's black and white and read all over?" - the old phrase linked to, of course, the habit of reading ( holding in one's two hands a folded bundle) a newspaper. The exhibit is a take-off and send-up as well as a sentimental recollection of a time when newspapers mattered. "Just chimney soot on chopped up trees" is the adage posted above artists' interpretations, or, rather, "manifestations" of the newspaper phenomenon from 1909 to 2009, in curatorial words on the flyleaf of the handsome book accompanying the show.