榆科 yu ke
Authors: Liguo Fu, Yiqun Xin & Alan Whittemore
Trees or shrubs, evergreen or deciduous. Winter buds with scales, rarely naked; axillary buds developed; terminal bud usually dying back early. Stipules usually membranous, caducous. Leaves simple, alternate or rarely opposite, usually distichous, petiolate; leaf blade pinnately veined, basally 3(or 5)-veined, margin entire or serrate. Inflorescences axillary. Flowers monochlamydeous, bisexual, or rarely unisexual or polygamous. Perianth lobes 4-9, imbricate or rarely valvate, persistent or caducous. Stamens usually equal in number to and opposite perianth lobes, opposite, basally adnate to tepals; filaments distinct; anthers 2-celled, longitudinally fissured. Pistil 2-carpellate; ovary superior, 1(or 2)-loculed; ovule 1, suspended, anatropous; integuments 2. Style very short; stigmas 2, linear. Fruit samara, drupes, or winged nutlets, apically usually with persistent stigmas. Endosperm scanty or absent; embryo erect, curved, or involute; cotyledons flat, curved, or flexed. Seedling epigeous.
About 16 genera and ca. 230 species: widespread in temperate and tropical areas; eight genera (one endemic) and 46 species (23 endemic) in China.
Recent research strongly suggests that the subfamily Celtidoideae (Aphananthe, Celtis, Gironniera, Pteroceltis, and Trema) is not the closest relative of the subfamily Ulmoideae (Hemiptelea, Ulmus, and Zelkova). It would probably be more accurate to exclude Celtidoideae from Ulmaceae, and move it to Cannabaceae, rather than treating it as a separate family, Celtidaceae. More data are needed before a stable, new classification of the Urticales can be produced. Until these data are available, it is more practical to retain the traditional circumscription of Ulmaceae.
Most species of this family yield fine timber, the cortex is a good substitute for hemp, the fruit are edible, and the seed oil is used medicinally and industrially. Many species of Ulmaceae are cultivated, and it is not always certain whether specimens are from wild or cultivated plants.
Fu Likuo, Chen Chiajui & Tang Yancheng. 1998. Ulmaceae. In: Chun Woonyong & Huang Chengchiu, eds., Fl. Reipubl. Popularis Sin. 22: 334–413.