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FOC | Family List | FOC Vol. 5 | Urticaceae

1. Urtica Linnaeus, Sp. Pl. 2: 983. 1753.

荨麻属 qian ma shu

Chen Jiarui (陈家瑞 Chen Chia-jui); Ib Friis, C. Melanie Wilmot-Dear

Herbs, rarely subshrubs, annual or perennial, armed with stinging hairs. Stems often 4-angled. Leaves opposite; stipules often persistent, interpetiolar, lateral, free or connate; leaf blade 3-5(-7)-veined, margin dentate or incised-lobed; cystoliths often punctiform, sometimes short botuliform. Inflorescences in axillary pairs; glomerules forming spikes, racemes, panicles, or rarely capitula, unisexual (plants monoecious or dioecious) or androgynous. Male flowers: perianth lobes 4, imbricate; stamens 4; rudimentary ovary cuplike. Female flowers: perianth lobes 4, free or connate, enlarged in fruit, enclosing achene, strongly unequal, outer 2 (lateral) smaller than inner 2 (dorsal-ventral) lobes. Ovary straight; stigma sessile or on short style, penicillate-capitate. ovule orthotropous. Achene straight, compressed, enclosed by persistent perianth. Seed erect, with scanty endosperm; cotyledons suborbicular, fleshy.

About 30 species: principally in N and S temperate regions, also in montane areas of tropics; 14 species (three endemic) in China.

The stem fibers are used to make ropes, the leaves are used as fodder, and the young shoots are used as a seasoning substitute for sorrel.

1 Stipules connate; inflorescences often branched.   (2)
+ Stipules mostly free (sometimes partly connate with 2-lobed apex on upper parts of plant in U. laetevirens); inflorescences unbranched or branched.   (6)
2 (1) Leaf blade ovate to lanceolate with margin dentate to doubly denticulate or doubly serrulate.   (3)
+ Leaf blade broadly ovate or subcordate, with margin lobed or rarely doubly denticulate.   (4)
3 (2) Leaf blade ovate to lanceolate, surface wrinkled when dried, margin sharply doubly serrulate; stem densely pubescent with many stinging hairs.   13 U. ardens
+ Leaf blade lanceolate or rarely narrowly ovate, surface nearly smooth when dried, margin crenate or inconspicuously double-denticulate to serrulate; stems sparsely pubescent with a few stinging hairs at least when old.   14 U. parviflora
4 (2) Stipules partly connate, apex 2-lobed or -cleft.   10 U. thunbergiana
+ Stipules wholly connate, apex obtuse.   (5)
5 (4) Leaf margin shallowly 5-7-lobed or palmately 3-lobed (lobes ± pinnately lobed again), lobe margin serrulate; inflorescences with a few short branches or almost unbranched.   11 U. fissa
+ Leaf margin usually 10- or more lobed, lobe margin doubly serrulate; inflorescences with many long branches.   12 U. mairei
6 (1) Plants usually dioecious; inflorescences branched.   (7)
+ Plants monoecious; inflorescences, at least female ones, unbranched or nearly so.   (8)
7 (6) Plants often with dense stinging and setose hairs; leaf blade ovate or lanceolate, base cordate; petiole 1/6-1/2 as long as leaf blade.   9 U. dioica
+ Plants with sparse stinging and setose hairs; leaf blade lanceolate to linear, base rounded or notched; petiole 1/15-1/5 as long as leaf blade.   8 U. angustifolia
8 (6) Inflorescences bisexual, containing proximal female flowers and distal male flowers.   (9)
+ Inflorescences often unisexual, containing either male or female flowers.   (11)
9 (8) Plant always annual; leaf blade broadly elliptic, apex obtuse-rounded; perianth lobes of female flowers connate at base, sparsely setulose along margin.   3 U. urens
+ Plant perennial; leaf blade ovate to lanceolate, apex acute to shortly acuminate; perianth lobes of female flowers connate 1/2 of length, subglabrous.   (10)
10 (9) Stipules 4-7 mm; leaf margin dentate or doubly serrate; achene ca. 0.8 mm.   1 U. atrichocaulis
+ Stipules ca. 2 mm; leaf margin incised-serrulate; achene ca. 1 mm.   2 U. taiwaniana
11 (8) Male inflorescences in distal axils; female perianth lobes without stinging hairs; cystoliths often botuliform.   7 U. laetevirens
+ Male inflorescences usually in proximal axils; female perianth lobes with stinging hairs; cystoliths often punctiform.   (12)
12 (11) Female perianth lobes membranous, inner pair 2 times as long as achene; petiole 0.2-0.5(-1.6) cm.   6 U. hyperborea
+ Female perianth lobes herbaceous, inner pair subequal to achene; petiole 1-8 cm.   (13)
13 (12) Achene smooth; female inflorescences in fruit drooping; outer 2 female perianth lobes 1/7-1/5 as long as inner 2.   9 U. dioica
+ Achene verrucose; female inflorescences in fruit erect or spreading; outer 2 female perianth lobes 1/4-1/2 as long as inner 2.   (14)
14 (13) Leaf margin 3-5-palmatisect or -palmatipartite, with pinnatisect lobes; female perianth lobes connate for 1/3 of length.   5 U. cannabina
+ Leaf margin coarsely dentate or sharply serrate; female perianth lobes connate at base only.   4 U. triangularis

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