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6. Stewartia Linnaeus, Sp. Pl. 2: 698. 1753.
紫茎属 zi jing shu
Cavanilla Salisbury (1796), not J. F. Gmelin (1792), nor Thunberg (1792); Hartia Dunn; Malachodendron Mitchell.
Shrubs or trees, evergreen or deciduous. Winter buds laterally compressed; bud scales 1 to several, imbricate. Petiole short, narrowly to widely winged, wing sometimes enclosing and concealing axillary and terminal buds; leaf blade ovate, lanceolate, or elliptic, papery to leathery, base cuneate to rounded, margin serrulate to serrate, apex acuminate, acute, or apiculate. Flowers axillary, solitary to several arranged in a short raceme, pedicellate. Bracteoles 2, close to sepals, persistent or rarely caducous. Sepals 5, imbricate, persistent, basally connate. Petals 5, white or yellowish white, imbricate, basally slightly connate. Stamens numerous, basally connate into a short tube and adnate to petals; anthers dorsifixed. Ovary superior, 5-loculed with 2-4(-7) ovules per locule, placentation axile but nearly basal; style connate or distinct. Capsule ovoid to conic, 5-ribbed, 5-loculed with (1 or)2-4 seeds per locule, loculicidal, enveloped by persistent sepals, apex acute or acuminately rostrate; pericarp splitting into 5 valves; columella abortive or ± apical 1/2 abortive. Seeds small, obovate, angular and wingless or planoconvex with a narrow marginal wing; testa crustaceous, shiny; embryo small, straight; cotyledons subrounded, clasping, embedded in copious fleshy endosperm.
About 20 species: China, Japan, Korea, Laos, Vietnam; E North America; 15 species (14 endemic) in China.
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| 1 |
Deciduous; winter bud with 2-11 scales; leaf blade papery or thinly leathery; petiole wingless or narrowly winged |
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(2) |
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Evergreen; winter bud without scales; leaf blade leathery or thickly leathery (papery to thinly leathery in S. calcicola); petiole distinctly winged |
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(4) |
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| 2 (1) |
Bracteoles reniform, not leaflike, 1/2 as long as sepals; sepals 0.6-1.2 cm, not leaflike; capsule 2-2.5 × 1.5-2 cm. |
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15 S. rubiginosa |
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Bracteoles not reniform, leaflike, ± equal to sepal length; sepals 1-2 cm, leaflike; capsule 1.2-2 × 1-1.5(-1.6) cm |
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(3) |
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| 3 (2) |
Bracteoles 2-2.5 × 1-1.3 cm; style ca. 1 cm; ovary tomentose throughout; capsule conical. |
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13 S. sinensis |
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Bracteoles (1.2-)1.5-2 × (0.6-)0.8-1.2 cm; style 1.6-1.8 cm; ovary basally densely sericeous, apically glabrous; capsule subglobose. |
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14 S. rostrata |
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| 4 (1) |
Flowers 2-5 in short racemes but sometimes solitary flowers also present |
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(5) |
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Flowers solitary |
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(9) |
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| 5 (4) |
Sepals longer than wide |
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(6) |
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Sepals as long as wide |
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(7) |
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| 6 (5) |
Leaf blade margin serrulate, apex long acuminate; bracteoles long obovate; sepals obovate to broadly elliptic, 12-15 × ca. 10 mm. |
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1 S. sinii |
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Leaf blade margin entire or apically with several serrations, apex obtuse; bracteoles and sepals lanceolate, sepals ca. 10 × 4 mm. |
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2 S. densivillosa |
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| 7 (5) |
Bracteoles lanceolate, as long as sepals. |
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3 S. laotica |
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Bracteoles ovate to broadly ovate (sometimes lanceolate in S. obovata), ca. 1/2 as long as sepals |
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(8) |
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| 8 (7) |
Leaf blade leathery, margin entire. |
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4 S. obovata |
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Leaf blade thickly leathery, margin serrate. |
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5 S. crassifolia |
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| 9 (4) |
Sepals orbicular to suborbicular, ± 1/2 as long as capsule |
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(10) |
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Sepals ovate, long ovate, or ovate-lanceolate, ± as long as capsule |
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(12) |
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| 10 (9) |
Bracteoles ca. 2/3 as long as sepals; capsule subglobose. |
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10 S. sichuanensis |
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Bracteoles ca. 1/2 as long as sepals; capsule conic |
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(11) |
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| 11 (10) |
Leaf blade oblong to narrowly oblong, adaxially glabrous, apex acuminate. |
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11 S. micrantha |
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Leaf blade oblong-elliptic, adaxially pubescent along midvein, apex abruptly acute to shortly acuminate |
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12 S. calcicola |
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| 12 (9) |
Sepals leaflike, apex acute |
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(13) |
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Sepals not leaflike, apex rounded to obtuse |
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(14) |
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| 13 (12) |
Sepals margin entire; ovary tomentose. |
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6 S. villosa |
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Sepals margin serrulate; ovary glabrous. |
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7 S. pteropetiolata |
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| 14 (12) |
Petiole 1.2-2.5 cm; leaf blade long ovate, thickly leathery; sepals long ovate, 9-12 mm, margin entire, outside pubescent. |
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8 S. cordifolia |
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Petiole ca. 1 cm; leaf blade oblong, leathery; sepals ovate, 7-8 mm, margin serrulate, outside velutinous. |
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9 S. medogensis |
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List of lower taxa
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Treatments in Other Floras @ www.efloras.org
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