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Urticaceae Jussieu

荨麻科 qian ma ke

Authors: Jiarui Chen, Prof. Qi Lin, Ib Friis, C. Melanie Wilmot-Dear & Alex K. Monro

Herbs, subshrubs, or shrubs, rarely trees, very rarely climbing, stems often fibrous, sometimes succulent. sometimes armed with stinging hairs; epidermal cells of leaves, sometimes stems, perianths mostly with prominent cystoliths punctiform to linear; Leaves alternate or opposite, stipules present, rarely absent; leaf blade simple. Inflorescences cymose, paniculate, racemose, spicate, or cluster-capitate, usually formed from glomerules, sometimes crowded on common enlarged cuplike or discoid receptacle, rarely reduced into a single flower. Flowers unisexual (plants monoecious or dioecious), rarely bisexual in partial flowers; actinomorphic, very small, (1-)4- or 5-merous, rarely perianth absent in female flowers. Calyx absent. Perianth lobes imbricate or valvate. Male flowers: stamens as many as and opposite to perianth lobes, filaments inflexed in bud; anthers 2-locular, opening lengthwise, rudimentary ovary often present. Female flowers: perianth lobes free or connate, usually enlarged in fruit and persistent, occasionally absent; staminodes scarious, opposite to the perianth lobes, or absent. Ovary rudimentary in male flowers, sessile or shortly stipitate, free or adnate to the perianth; 1-locular, ovule solitary, erect from the base; style simple, or absent; stigma diverse, capitate, penicillate-capitate (brushlike), subulate, filiform, ligulate, or peltate. Fruit usually a dry achene, sometimes a fleshy drupe, often enclosed by the persistent perianth. Seed solitary, endosperm usually present; embryo straight; cotyledons ovate elliptical or orbicular.

About 47 genera and 1300 species: most numerous in wet tropical regions, extending into temperate regions; 25 genera and 341 species (163 endemic, one introduced) in China.

Plants in this family have numerous uses. The stem fiber of some genera and species is of high quality and used to make cloth, fishing nets, and ropes and for some industrial materials. In central and southern China, Boehmeria nivea is widely cultivated for ramie fiber and Girardinia diversifolia subsp. triloba is widely cultivated for “red huo ma” fiber. Boiled young shoots of Girardinia, Laportea, and Urtica are eaten as vegetables. Some species are used in local Chinese medicine. Pellionia repens, Pilea cadierei, P. microphylla, and P. peperomioides, among other species, are widely cultivated as ornamentals in China and elsewhere. Some genera, such as Elatostema, Pellionia, and Pilea, occur frequently in shady, moist habitats of subtropical forests and become dominant elements of the forest floor vegetation. Plants of the first five genera belong to tribe Urticeae, which is usually characterized by the distinctive stinging hairs.

Chen Chiajui & Wang Wentsai. 1995. Urticaceae. In: Wang Wentsai & Chen Chiajui, eds., Fl. Reipubl. Popularis Sin. 23(2): 1–404.

1 Filaments of stamens erect in bud; shrubs or woody climbers.   18 Poikilospermum
+ Filaments of stamens inflexed in bud; usually not woody climbers.   (2)
2 (1) Plants armed with stinging hairs; female flowers without staminodes.   (3)
+ Plants without stinging hairs; female flowers with or without staminodes.   (7)
3 (2) Leaves opposite; perianth lobes of female flowers free, lateral pair outer and much smaller than dorsiventral pair.   1 Urtica
+ Leaves alternate; perianth lobes of female flowers connate or if free then not as above.   (4)
4 (3) Stipules interpetiolar; achene straight, sessile; stigma penicillate-capitate; slender herb to 40 cm.   2 Nanocnide
+ Stipules intrapetiolar; achene strongly oblique, stipitate; stigma filiform, ligulate, or subulate; trees, shrubs or usually robust herbs.   (5)
5 (4) Female perianth with 3 lobes fused and the 4th absent or reduced to a bristle; robust herb with longest stinging hairs more than 5 mm.   5 Girardinia
+ Female perianth lobes 4, dorsal lobe largest, ventral lobe smallest, joined at base only, never bristle-like; ± woody shrub or tree or herbs with longest stinging hairs less than 5 mm.   (6)
6 (5) Stipules completely joined, apex entire; trees or shrubs; pedicels of female flowers absent or terete, not winged in fruit.   4 Dendrocnide
+ Stipules 2-fid at apex; herbs or subshrubs; pedicels of female flowers always present, winged in fruit.   3 Laportea
7 (2) Cystoliths usually linear or fusiform; stigma sessile, penicillate-capitate; perianth lobes of female flowers free or connate at base, staminodes present (except in Procris).   (8)
+ Cystoliths dotlike or very short blunt rods (botuliform); stigma often on a style, mostly linear, less often penicillate-capitate; perianth lobes of female flowers usually connate into a tube, rarely strongly reduced, or absent, staminodes absent.   (12)
8 (7) Leaves opposite, rarely spirally alternate and then leaf blade peltate; leaf blade usually symmetric.   (9)
+ Leaves alternate or very strongly heterophyllous with 1 leaf of the pair reduced to a nanophyll very much smaller than the other, leaves usually distichous; leaf blade usually asymmetric.   (10)
9 (8) Flowers usually forming loose cymes or cymose panicles, sometimes spikes or in clusters; achene without crested appendix at apex.   6 Pilea
+ Flowers inserted on discoid or concave, fleshy receptacle; achene with crested or U-shaped appendix at apex.   7 Lecanthus
10 (8) Perianth lobes of female flowers usually 4 or 5, much shorter than ovary, or strongly reduced, not corniculate at apex; achene 6-10-ribbed; male inflorescences usually with receptacle, rarely cymose; female inflorescences with discoid receptacle and bracteoles along margin.   9 Elatostema
+ Perianth lobes of female flowers 3-5, longer than ovary, usually corniculate below apex; achene tuberculate or striate, rarely smooth, never ribbed; male inflorescences cymose; female inflorescences cymose or captitate on globose receptacle.   (11)
11 (10) Female inflorescences cymose, rarely with discoid receptacle and involucre; perianth lobes of female flowers (4 or)5; staminodes present.   8 Pellionia
+ Female inflorescences capitate on globose receptacle, but without involucre; perianth lobes of female flowers 3 or 4; staminodes absent.   10 Procris
12 (7) Stipules absent; flowers sometimes bisexual, each subtended by 1 or more leaflike bracts longer than the flower, contrasting with the chaffy brown perianth and glossy black achene.   24 Parietaria
+ Stipules present; flowers unisexual, bracts and flowers not as above.   (13)
13 (12) Inflorescence enclosed within involucre, usually bisexual with several male flowers surrounding 1 or 2 female flowers; male flower with 1 stamen; female flower without perianth.   25 Droguetia
+ Inflorescence without involucre, often unisexual; male flower with 3-5 stamens; female flower with tubular perianth around ovary.   (14)
14 (13) Leaves opposite.   (15)
+ Leaves alternate.   (20)
15 (14) Leaf blade margin entire.   (16)
+ Leaf blade margin serrate or dentate.   (17)
16 (15) Male buds truncate, perianth with annular, often villous, crown formed from transverse crests of lobes; leaf blade 3-veined from base.   15 Gonostegia
+ Male flowers without this combination of characters; leaf blade with at least 2 major lateral veins arising clearly above base.   14 Pouzolzia
17 (15) Stigma ovoid-capitate, on short style; stipules persistent, reflexed at flowering; slender stoloniferous herb.   13 Chamabainia
+ Stigma elongated; stipules often deciduous; shrub or herb, not stoloniferous.   (18)
18 (17) Stigma minute, less than 0.5 mm, hooked, persistent; fruit symmetrically enlarged at apex; inflorescences paired at nodes, sessile, ± globose, very dense with base partly enveloping stem.   16 Cypholophus
+ Stigma relatively long, variously curved [but if hooked then more than 1 mm], sometimes deciduous; fruit ± symmetric at apex, often winged; inflorescence various, often pedunculate, if sessile then base not enveloping stem.   (19)
19 (18) Achene not lustrous, remaining attached to perianth; stigma persistent.   12 Boehmeria
+ Achene lustrous, easily detached from perianth; stigma usually deciduous.   14 Pouzolzia
20 (14) Stigma filiform or ligulate.   (21)
+ Stigma penicillate, peltate or ringlike.   (24)
21 (20) Stigma ligulate.   11 Archiboehmeria
+ Stigma filiform.   (22)
22 (21) Female perianth fleshy at maturity, apex with tiny, entire opening, lobes completely fused; style deciduous.   19 Pipturus
+ Female perianth not fleshy, apex minutely 2-toothed; style often persistent.   (23)
23 (22) Achene not lustrous, remaining attached to perianth; stigma persistent.   12 Boehmeria
+ Achene lustrous, easily detached from perianth; stigma usually deciduous.   14 Pouzolzia
24 (20) Inflorescence elongated with short lateral branches, all axes completely hidden by very closely spaced flowers; stigma ringlike.   17 Sarcochlamys
+ Inflorescence globose or nearly so or, if more elongated and branched then axes exposed between discrete glomerules of flowers; stigma peltate or penicillate.   (25)
25 (24) Stigma peltate with long ciliate hairs along margin; achene adnate to thinly fleshy perianth, surrounded at base or almost wholly enclosed by discoid or cuplike fleshy receptacle.   20 Oreocnide
+ Stigma penicillate; achene without fleshy receptacle.   (26)
26 (25) Perianth of female flowers inconspicuous, connate into a shallow pocket or absent; leaves usually discolorous, abaxially white tomentose.   23 Maoutia
+ Perianth of female flowers conspicuous, connate into a tube; leaves sometimes concolorous.   (27)
27 (26) Female perianth small, cupular, 4 or 5-lobed or -toothed, adnate to base of ovary; inflorescences paired, unbranched pedunculate heads.   22 Leucosyke
+ Female perianth enclosing ovary, tube obovoid or jug-shaped, mouth contracted, very minutely 3- or 4-toothed, in fruit often enlarged, fleshy, and adnate to ovary, rarely membranous and free; inflorescences often branched.   21 Debregeasia

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