Michael Pollan's best-selling book, Botany of Desire, is now a film, and you can watch it online, courtesy of PBS. (Click to watch complete film.) The film takes you inside our relationship with the plant world, and shows "how four familiar species -- the apple, the tulip, cannabis and the potato -- evolved to satisfy our yearnings for sweetness, beauty, intoxication and control." According to a piece in The San Francisco Chronicle, it took eight years to pull together the funding for the film, and that's simply because marijuana was in the mix. The film runs close to two hours. The preview is above, the full film is here. For more films, please visit our collection of Free Movies Online.