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Ulmaceae Mirbel

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.


1 Fruit dry, broadly winged at least on one side.   (2)
+ Fruit drupes (scarcely fleshy in Zelkova), not winged.   (4)
       
2 (1) Flowers unisexual; anthers apically pubescent; leaves 3-veined from base; secondary veins curving inward, not reaching margin.   3 Pteroceltis
+ Flowers bisexual or polygamous; anthers apically glabrous; leaves pinnately veined; secondary veins straight, each ending in a marginal tooth.   (3)
       
3 (2) Fruit symmetric, winged on both sides; seed round; branchlets without spines.   1 Ulmus
+ Fruit asymmetric, winged only on one side; seed elongate and curved; branchlets with spines.   2 Hemiptelea
       
4 (1) Leaf blade 3(or 5)-veined from base.   (5)
+ Leaf blade pinnately veined.   (7)
       
5 (4) Lateral veins extending to margin, each ending in a tooth (Aphananthe aspera).   6 Aphananthe
+ Lateral veins veins anastomosing before reaching margin.   (6)
       
6 (5) Flowers unisexual (polygamous in Trema cannabina), shortly pedicellate; fruit 1.5-4 mm in diam., with persistent tepals and stigmas, stalk short; leaf blade margin denticulate.   7 Trema
+ Flowers polygamous, long pedicellate; fruit 5-15 mm in diam., without persistent tepals and stigmas, stalk long; leaf blade margin entire or serrate.   8 Celtis
       
7 (4) Flowers polygamous; leaf blade serrate to crenate; secondary veins extending to margin, each ending in a tooth.   4 Zelkova
+ Flowers unisexual; leaf blade entire, shallowly serrate, or denticulate; secondary veins anastomosing before reaching margin.   (8)
       
8 (7) Stipules usually basally connate, enclosing bud, leaving a single transverse scar that completely encircles stem at each node.   5 Gironniera
+ Stipules not connate, nor enclosing bud, leaving two small transverse scars one on each side of leaf base.   (9)
       
9 (8) Leaf blade narrowly ovate, ovate, or oblong-lanceolate, margin usually entire or occasionally inconspicuously serrate; drupe 13-20 mm (Aphananthe cuspidata).   6 Aphananthe
+ Leaf blade elliptic-lanceolate to narrowly lanceolate, margin denticulate; drupe 1.5-2.5 mm (Trema levigata).   7 Trema

Lower Taxa


 

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