4. Houpoëa N. H. Xia & C. Y. Wu, Fl. China. 7: 64. 2008.
厚朴属 hou po shu
Replaced synonym: Magnolia sect. Rytidospermum Spach, Hist. Nat. Vég. Phan. 7: 474. 1839, not Rhytispermum Link, Handbuch 1: 579. 1829, nor Rhytidospermum Schultz Bipontinus in Webb & Berthelot, Hist. Nat. Iles Canaries 3(2, 2): 277. 1844, nor Rytidosperma Steudel, Syn. Pl. Glum. 1: 425. 1854.
Trees or shrubs, deciduous. Bark usually gray, smooth. Twigs with annular stipular scar. Stipules membranous, adnate to petiole, leaving stipular scar on petiole. Leaves spirally arranged, often fascicled and pseudowhorled, folded in bud, erect when young; leaf blade membranous or thickly papery, margin entire or rarely shallowly 2-lobed at apex. Flowers terminal, solitary, bisexual, large, fragrant. Spathaceous bract 1. Tepals 9-12, in 3 or 4 whorls, usually white, subequal. Stamens caducous; filaments flat; connective exserted and forming a short mucro; anthers dehiscing introrsely. Gynoecium without a gynophore; carpels numerous, distinct; ovules usually 2(-4) per carpel; styles curved outward, adaxially papillate. Fruit usually cylindric when mature; mature carpels distinct, leathery or subwoody, dehiscing along dorsal sutures, persistent on torus, apex long beaked.
Nine species: E North America and temperate regions of SE Asia; three species (one endemic, one introduced) in China.