Ride along with hemp-happy narrator Woody Harrelson as he follows marijuana from its first trek over the Mexican border in the early 20th century to its current illegal status in America. Played-out propaganda film footage seems fresh when juxtaposed against clips of ganja’s public enemy No. 1: Henry Anslinger, the granddaddy of the narc squad. Fringe director Ron Mann includes many hilarious glimpses at suburbia — a ’70s mom goofing on pot brownies — but the lack of focus on inner-city reality is a stoned-cold oversight. That omission aside, Grass is a damn fine score.