Pierre-Joseph Redoute, Plum Branches Intertwined, 1802-04, watercolor on vellum. (Images Courtesy Of Yale Center For British Arts.)When Charles Ryskamp was interviewed in 2004, he found the reporter's questions about his background so tedious he snapped: "I don't want this to be an obituary." Ryskamp needn't have worried. The one-time director of both the Morgan Library and Museum and the Frick Collection died on March 26, 2010, with the best possible remembrance of his life and career on display at the Yale Center For British Art. Varieties of Romantic Experience: Drawings from the Collection of Charles Ryskamp, an exhibit of 200...