圆叶乌桕Sapium rotundifolium Hemsl.

别名：山乌桕;圆叶乌臼;米桕芭;红叶树;雁来红;大叶乌桕;圆叶桕木;

科名：大戟科 Euphorbiaceae

属名：乌桕属 Sapium

《中国植物志》第44(3)卷017页
  4.圆叶乌桕（中国树木分类学）图版3: 5-7
  Sapium rotundifolium Hemsl. in Journ. Linn. Soc. Bot. 26: 445. 1894; Pax et Hoffm. in Engl. Pflanzenr. 52 (IV. 147. V.): 241 1912; Dunn et Tutcher in Kew Bull. Misc. Inform. add. ser. 10: 241. 1912; Gagnep. in Lecomte, Fl. Gen. Indo-Chine 5: 400. 1926; Hand. -Mazz. Symb. Sin. 7: 212. 1931; Rehd. in Journ. Arn. Arb. 14: 234. 1933;陈嵘, 中国树木分类学613. 1937; S. K. Lee in Acta Phytotax. Sin. 5: 120. 1956;中国高等植物图鉴2: 616.图1962, 1972; Y. C. Tseng in Acta Phytotax. Sin. 200): 106. 1982. ——Baccaurea esquirolii Levl. Fl. Kouy-Tchoeu 159. 1914.——Sapium rotundifolium Hemsl. var. obcordatum S. K. Lee in Acta Phytotax. Sin. 5: 121. 1956.
  灌木或乔木，高3-12米，全部无毛；小枝粗壮而节间甚短。叶互生，厚，近革质，叶片近圆形，长5-11厘米，宽6-12厘米，顶端圆，稀凸尖，亦偶有不同深浅的凹缺者，基部圆、截平至微心形，全缘，腹面绿色，背面苍白色；中脉在背面显著凸起，侧脉10-15对，从中脉平展发出或略向上弯拱，离缘4-6毫米网结，网脉明显；叶柄圆柱形，纤细，长3-7厘米，顶端具2腺体；托叶小，腺体状，长常为宽的1/2。花单性，雌雄同株，密集成顶生的总状花序，雌花生于花序轴下部，雄花生于花序轴上部或有时整个花序全为雄花。雄花：花梗圆柱形，长1-3毫米；苞片卵形，长和宽近相等约2毫米，顶端锐尖，边缘流苏状，基部两则各具1腺体，每一苞片内有3-6朵花；小苞片狭卵形，长和宽近相等约0.8毫米，顶端撕裂状；花萼杯状，3浅裂，裂片圆，有细齿；雄蕊2枚，罕为1或3枚，花药圆形，花丝极短。雌花：花梗比雄花的粗壮，长约2毫米，苞片与雄花的相似，每一苞片内仅有1朵花；花萼3深裂几达基部，裂片阔卵形，宽1-1.2毫米，顶端短尖，边缘具细齿；子房卵形，花柱3，基部合生，柱头外卷。蒴果近球形，直径约1. 5厘米；分果爿木质，自宿存的三角柱状的中轴上脱落；种子久悬于中轴上，扁球形，直径约5毫米，顶端具一雅致的小凸点，腹面具1纵棱，外面薄被蜡质的假种皮。花期4-6月。
  分布于云南、贵州、广西、广东和湖南。喜生于阳光充足的石灰岩山地，为钙质土的指示植物。越南北部也有。模式标本采自广东。

《Flora of China》 Vol. 11 (2008)
Triadica rotundifolia  (Hemsley) Esser
圆叶乌桕   yuan ye wu jiu
Sapium rotundifolium Hemsley, J. Linn. Soc., Bot. 26: 445. 1891; Baccaurea esquirolii H. Léveillé; S. rotundifolium var. obcordatum S. K. Lee.
Trees up to 12 m tall, glabrous; branchlets robust. Leaves alternate; stipules small, glandular, caducous; petioles 3-7 cm, with 1 gland at apex; leaf blade subrotund, 5-11 × 6-12 cm, base rounded to shallowly cordate, margin entire, apex rounded, rarely acute or incised; lateral veins 10-15 pairs. Flowers unisexual, monoecious, densely fascicled in terminal racemes, female in lower part, male in upper part, sometimes male throughout. Male flowers: pedicels cylindric, 1-3 mm; bracts ovate, ca. 2 × 2 mm, margins fimbriate, base bilateral, each with 1 gland; bracteoles narrowly ovate, less than 1 mm; calyx cupular, shallowly 3-lobed; stamens (1 or)2(or 3); filaments shorter; anthers subglobose. Female flowers: pedicels robust, ca. 2 mm; calyx 3-lobed, lobes broadly ovate, ca. 1 mm, margins serrulate; ovary ovate, 3-lobed; styles 3, connate at base; stigma revolute. Capsules subglobose, 8-10 mm in diam. Seeds oblate, ca. 5 mm in diam., with waxy arils. Fl. Apr-Jun, fr. Jul-Oct.
Limestone montane forests; 100-500 m. Guangdong, Guangxi, Guizhou, Hunan, Yunnan [N Vietnam].