52. Mitracarpus Zuccarini in Schultes & J. H. Schultes, Mant. 3: 210 ["Mitracarpum"], 399. 1827.
盖裂果属 gai lie guo shu
Authors: Tao Chen & Charlotte M. Taylor
Herbs [to small shrubs], annual or perennial, unarmed. Raphides present. Leaves opposite, subsessile or sessile, without domatia; stipules persistent, interpetiolar and fused to leaf bases or petioles, truncate to rounded, setose. Inflorescences terminal and/or axillary, glomerulate or capitate, several to many flowered, sessile, sometimes immediately subtended by 1 or 2 pairs of leaves, bracteate. Flowers sessile, bisexual, monomorphic. Calyx limb deeply 4(or 5)-lobed; lobes usually unequal in pairs, usually with hyaline margins. Corolla white, salverform or funnelform, inside glabrous or pubescent in throat; lobes 4, valvate in bud. Stamens 4, inserted in corolla throat, included or exserted; filaments developed; anthers dorsifixed. Ovary 2-celled, ovules 1 in each cell on peltate axile placentas attached at middle of septum; stigmas 2, linear, usually exserted. Fruit capsular, subglobose to somewhat dicoccous, with dehiscence circumscissile around equator, with apical valve or "lid" deciduous and basal portion persistent, papery to cartilaginous, with calyx limb persistent or deciduous on lid; seeds 2, medium-sized, oblate to rounded, on ventral (i.e., adaxial) face with cruciform (i.e., X-shaped) scar; endosperm fleshy; cotyledon leaflike; radicle hypogeous.
About 30 species: widespread in tropical and subtropical Central, North, and South America and the Antilles, with one species widely naturalized in tropical Africa, Asia, Australia, and Pacific islands; one species (introduced) in China.
This genus is frequently overlooked even in its native range, but the circumscissile capsules, seeds with a distinctive cruciform scar, leaves scabrous to the touch on the upper surface, and well-developed calyx lobes with hyaline erose margins are distinctive. W. C. Ko (in FRPS 71(2): 210. 1999) described the ovary as sometimes 3-celled; this condition is not otherwise known in Mitracarpus and has not been reconfirmed, although it does characterize the very similar, likewise adventive genus Richardia.