Description from Flora of China
Shrubs or small trees, deciduous or evergreen. Branchlets dichotomous, quadrangular to subterete, with oil cells; buds covered with scales or naked and hidden [or not hidden] by base of petiole. Stipules absent. Leaves opposite, simple, petiolate; leaf blade pinnately veined, margin entire or subentire. Flowers bisexual, axillary or terminal on branchlets, usually solitary, radially symmetric, usually fragrant, generally appearing before leaves for deciduous taxa, undifferentiated into calyx and corolla but sometimes tepals of more than one form. Pedicel short. Tepals 15-27[-30], yellow, yellowish white, or white flushed pink [or brownish red], spirally arranged on outer surface of a cup-shaped or urceolate receptacle, shape variable, outer usually bractlike, inner petaloid. Stamens numerous, spirally inserted on apical surface of receptacle, in 2 series, outer series fertile, inner series aborted; fertile stamens spirally arranged; filaments short and free; anthers 2-locular, incumbent against connective, extrorse, dehiscing lengthwise by slits; connective exserted, apex apiculate; staminodes linear, linear-lanceolate, or oblong, pubescent or puberulous. Carpels few to numerous, distinct, spirally arranged on basal inner surfaces of hollow cuplike receptacle, 1-loculed; ovules 2 per carpel but usually 1 abortive, anatropous; styles filamentous and extended. Pseudocarp polygynaecial, fleshy when young but becoming dry and sometimes woody, composed of achenes contained within an expanded torus, apex with appendages from persistent staminodes. Achenes 1-seeded; endosperm little or absent; embryo large; cotyledons convolute, foliose.
Sometimes the monotypic genus Idiospermum Blake, endemic to Queensland, Australia, is included in Calycanthaceae (see S. L. Zhou et al., Molec. Phylogenetic. Evol. 39: 1-15. 2006).
Li Ping-t’ao. 1979. Calycanthaceae. In: Tsiang Ying & Li Ping-t’ao, eds., Fl. Reipubl. Popularis Sin. 30(2): 1-10.
Two genera and nine species: E Asia and North America; two genera (one endemic) and seven species (all endemic) in China.
(Authors: Li Bingtao (李秉滔 Li Ping-tao); Bruce Bartholomew)