97. Xanthophytum Reinwardt ex Blume, Bijdr. 989. 1826.
岩黄树属 yan huang shu shu
Authors: Tao Chen & Charlotte M. Taylor
Paedicalyx Pierre ex Pitard; Xanthophytopsis Pitard.
Small trees, shrubs, or subshrubs, sometimes unbranched (i.e., monocaulous), unarmed, often fleshy; young growth usually densely sericeous to lanate, hirsute, or tomentose with trichomes drying golden yellow to ferruginous. Raphides present. Leaves opposite, isophyllous [or sometimes markedly anisophyllous], without domatia; stipules persistent or deciduous, interpetiolar, generally triangular or somewhat leaflike, sometimes markedly parallel-veined or -fibrous, entire or 2-lobed. Inflorescences axillary, cymose to paniculate or subcapitate, several to many flowered, sessile to pedunculate, bracteate or bracts reduced. Flowers sessile to pedicellate, bisexual, distylous or monomorphic, at least sometimes fragrant. Calyx limb shallowly to deeply 5-lobed; lobes sometimes unequal on an individual flower. Corolla white, yellow, or purple, tubular to funnelform, inside with pubescent ring in upper part of tube; lobes 5, valvate in bud. Stamens 5, exserted or included, inserted near middle to base of corolla tube; filaments reduced to developed; anthers apparently dorsifixed. Ovary 2-celled, ovules numerous in each cell on peltate placentas attached at middle of septum; stigmas clavate to 2-lobed, included or exserted. Infructescences often with peduncle, axes, and pedicels elongating notably. Fruit indehiscent, schizocarpous, or capsular, ovoid to subglobose, dry, with calyx limb persistent or deciduous, sometimes splitting septicidally into 2 indehiscent mericarps or loculicidally dehiscent valves, these each 1-celled, ellipsoid to plano-convex, each with numerous seeds; seeds small, angled, smooth, often brown.
About 30 species: China, Indonesia (including Borneo, with most of the species), Laos, Malaysia, New Guinea, Pacific islands (Fiji), Philippines, Vietnam; four species in China.
Xanthophytum was reviewed for China by Chun and F. C. How (Sunyatsenia 4: 10-15. 1939, as Paedicalyx) and then by H. S. Lo (Bull. Bot. Res., Harbin 6(4): 21-33. 1986), who formally synonymized Xanthophytopsis and Paedicalyx in this region based on previous comments by Bakhuizen but making the necessary combinations. Axelius (Blumea 34: 425-497. 1990) provided the only comprehensive review of Xanthophytum. She recognized four types of trichomes characteristic of the genus (loc. cit.: 427, f. 1); also notable in Xanthophytum are the fruit with numerous tiny seeds apparently enclosed in drupaceous locules or mericarps, and the stamen filaments that are often fused to the corolla only at the base and appear free or nearly free. Several authors have described the fruit as drupaceous and splitting, but the fruit morphology apparently corresponds better to schizocarpous in the terminology used in this treatment. Axelius observed also that distyly in Xanthophytum was apparently not noted by Chinese authors, resulting in somewhat confused descriptions of floral morphology.
