Plants too, both real and invented, play many roles in literature and film.[65] Plants' roles may be evil, as with the triffids, carnivorous plants with a whip-like poisonous sting as well as mobility provided by three foot-like appendages, from John Wyndham's 1951 science fiction novel The Day of the Triffids, and subsequent adaptations for film and radio.[66] J. R. R. Tolkien's fictional world Middle-earth features many named kinds of plant, including the healing herb athelas[67] the yellow star-flower elanor which grows in special places such as Cerin Amroth in Lothlórien,[68] and the tall mallorn tree[69] of the elves. Tolkien names several individual trees of significance in the narrative, including the Party Tree in the Shire with its happy associations,[69] and the malevolent Old Man Willow[70] in the Old Forest.[71] Trees feature in many of Ursula K. Le Guin's books, including the forest world of Athshe and the Immanent Grove[72] on Roke in the Earthsea series, to such an extent that in her introduction to her collection The Wind's Twelve Quarters, she admits to "a certain obsession with trees" and describes herself as "the most arboreal science fiction writer".[73] James Cameron's 2009 film Avatar features a giant tree named Hometree, the sacred gathering place of the humanoid Na'vi tribe; the interconnected tree, tribe and planet are threatened by mining: the tribe and the film's hero fight to save them.[74] Trees are common subjects in poetry, including Joyce Kilmer's 1913 lyric poem named "Trees".[75][76] Flowers, similarly, are the subjects of many poems by poets such as William Blake, Robert Frost, and Rabindranath Tagore.[77]