Robert Duncan, 69, a little known but widely praised lyric poet. Duncan was the author of 14 books of poetry and a collection of essays from 1959 to the recently published "Ground Work II: In the Dark," a follow-up to his 1984 volume, "Ground Work: Before the War," which was nominated for a National Book Critics Circle Award. Among his best known works were "The Opening of the Field" and "Roots and Branches." He was influenced by Ezra Pound and followed Pound's so-called "mystical directness." "He wrote very difficult but very beautiful poetry," said his New York publisher, Peter Glassgold, editor of New Directions. Duncan, a native of Oakland, Calif., was a Guggenheim fellow in 1963, received Poetry magazine's Harriet Monroe Memorial prize in 1961 and the first-ever National Poetry Award in 1985. In San Francisco on Wednesday of a heart attack.