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4. Amaranthus Linnaeus, Sp. Pl. 2: 989. 1753.
苋属 xian shu
Herbs annual. Stem erect or decumbent. Leaves alternate, petiolate, margin entire. Flowers unisexual, on same plant or not, sessile, clustered at axils and at apex, in solitary or complex thyrsoid structures; each flower with 1 bract and 2 bracteoles, scarious. Tepals 5, rarely 1-4, erect or obliquely spreading, sometimes indurate at base after anthesis, green, equal or subequal, membranous. Stamens 5, rarely 1-4; filaments free, filiform, pseudostaminodes absent; anthers 2-loculed. Ovary with 1 erect ovule; style short or absent; stigmas 2 or 3, persistent, subulate or linear. Utricles globose or ovoid, laterally compressed, membranous, dehiscent by lid, dehiscing irregularly or falling off together with perianth and indehiscent. Seeds black or brown, globose or lenticular, without aril.
About 40 species: worldwide; 14 species (one endemic, at least eight introduced) in China.
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| 1 |
Tepals 3, rarely 2 or 4; stamens 3; utricles indehiscent. |
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(2) |
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Tepals 5; stamens 5, rarely 2 or 3; utricles usually dehiscent by lid. |
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(7) |
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| 2 (1) |
Fruit indehiscent. |
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(3) |
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Fruit circumscissile. |
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(4) |
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| 3 (2) |
Stem erect, somewhat branched; utricles very rugose. |
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13 A. viridis |
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Stem ascending, much branched (frequently at base); utricles smooth or slightly rugose. |
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14 A. blitum |
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| 4 (2) |
Tepals 4, rarely 5. |
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12 A. blitoides |
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Tepals 3, rarely 2. |
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(5) |
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| 5 (4) |
Tepals conspicuously longer than fruit. |
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9 A. tricolor |
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Tepals ca. as long as or shorter than fruit. |
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(6) |
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| 6 (5) |
Stamens longer than perianth; bracts conspicuously longer than perianth. |
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10 A. albus |
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Stamens shorter than perianth; bracts ca. as long as or shorter than perianth. |
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11 A. roxburghianus |
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| 7 (1) |
Stamens 2, rarely 3. |
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8 A. taishanensis |
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Stamens 5. |
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(8) |
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| 8 (7) |
Armed at leaf axils; bract often becoming 2 spines, rarely 1. |
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7 A. spinosus |
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Unarmed at leaf axils; bract not becoming spiny. |
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(9) |
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| 9 (8) |
Plants hairy. |
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(10) |
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Plants glabrous or nearly so. |
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(11) |
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| 10 (9) |
Fruit enveloped in persistent perianth. |
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5 A. retroflexus |
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Fruit longer than perianth. |
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6 A. hybridus |
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| 11 (9) |
Complex thyrsoid structures pendulous; bracts and bracteoles inconspicuously pointed at apex. |
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1 A. caudatus |
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Complex thyrsoid structures erect; bracts and bracteoles conspicuously pointed at apex. |
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(12) |
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| 12 (11) |
Herbs high, to 2 m tall; leaf blade paler and pubescent on abaxial veins. |
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2 A. patulus |
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Herbs short, 0.1-0.8 m tall; leaf blade not pale, glabrous. |
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(13) |
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| 13 (12) |
Tepals ca. as long as or longer than fruit; bracts ca. 2 × as long as perianth. |
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3 A. hypochondriacus |
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Tepals distinctly shorter than fruit; bracts ca. 1.5 × as long as perianth. |
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4 A. cruentus |
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List of lower taxa
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Treatments in Other Floras @ www.efloras.org
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