| 1 |
Leaf blade narrowly oblong-elliptic or oblanceolate, base usually not decurrent (except in R. hookeri). |
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(2) |
| + |
Leaf blade elliptic, obovate or sub-orbicular, base sometimes decurrent, then with petiole narrowly winged. |
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(9) |
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| 2 (1) |
Leaf blade 9–17 × 3–6 cm; inflorescence rachis 5–15 mm. |
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(3) |
| + |
Leaf blade 3–8 × 1.5–2.5 cm; inflorescence rachis 3–5 mm. |
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(6) |
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| 3 (2) |
Petiole 0.5–1 cm, stipitate-glandular and dendroid-hairy; pedicel slender, 0.5–1 cm; calyx ca. 3 mm. |
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454 Rhododendron faucium |
| + |
Petiole 1.5–3 cm, glabrous; pedicel stout, 1.5–2 cm; calyx 5–8 mm. |
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(4) |
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| 4 (3) |
Petiole cylindric; inflorescence usually 2–3-flowered; corolla 5.5–7 cm; ovary and the base of
style pubescent and glandular. |
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455 Rhododendron megalanthum |
| + |
Petiole with adaxial surface flat; inflorescence usually 10–15-flowered; corolla 3.5–4.5 cm;
ovary and style glabrous. |
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(5) |
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| 5 (4) |
Lateral leaf veins 11–13 each side of midrib, abaxially with stout beadlike fasciculate hairs,
corolla deep crimson or rose pink. |
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456 Rhododendron hookeri |
| + |
Lateral leaf veins 15–18 each side of midrib, abaxially with slender fasciculate hairs; corolla
pale rose or pinkish. |
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452 Rhododendron hylaeum |
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| 6 (2) |
Corolla crimson; calyx 8–12 mm, irregularly split; pedicel 5–8 mm; ovary and style glabrous. |
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449 Rhododendron populare |
| + |
Corolla white or rose to crimson; calyx 2–8 mm; pedicel 10–25 mm; ovary and style glandular. |
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(7) |
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| 7 (6) |
Petiole ca. 5 mm; stamen filaments tomentose at base; style glabrous towards tip. |
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461 Rhododendron eurysiphon |
| + |
Petiole 8–10 mm; stamen filaments glabrous; style glandular to tip. |
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(8) |
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| 8 (7) |
Leaf blade 5–8 × 2–2.5 cm; pedicel slender, 2–3 cm; corolla 3.5–4 cm. |
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448 Rhododendron cerasinum |
| + |
Leaf blade 4–5 × ca. 1.5 cm; pedicel short, ca. 1.5 cm; corolla ca. 2.5 cm. |
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447 Rhododendron bonvalotii |
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| 9 (1) |
Leaf blade suborbicular, base rounded or cordate; abaxial surface sometimes glaucous, often with some
red stipitate glands. |
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(10) |
| + |
Leaf blade obovate, broadest above the middle, base cuneate, rarely rounded; abaxial surface not glaucous, glabrous or with brownish indumentum. |
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(12) |
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| 10 (9) |
Petiole slender, cylindric, 1–1.5 mm wide; calyx 4–7 mm; ovary tomentose and glandular. |
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451 Rhododendron viscidifolium |
| + |
Petiole thick or flat, 2–4 mm wide; calyx 0.5–1.2 cm, red; ovary only glandular. |
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(11) |
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| 11 (10) |
Petiole cylindric, ca. 2 mm wide; leaf blade 4–7 cm; corolla crimson; filaments tomentose at base. |
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450 Rhododendron thomsonii |
| + |
Petiole flat, 3–4 mm wide; leaf blade 8–13 cm; corolla white or pink; filaments glabrous. |
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458 Rhododendron cyanocarpum |
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| 12 (9) |
Style glandular, with dendroid hairs along whole length. |
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453 Rhododendron ramipilosum |
| + |
Style glabrous. |
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(13) |
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| 13 (12) |
Abaxial leaf surface thinly persistently fawn-farinose; inflorescence 3–7-flowered, rachis
conical, 1–2 mm; petiole 5–10 mm, not winged. |
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460 Rhododendron stewartianum |
| + |
Abaxial leaf surface glabrous or pubescent along midrib only; inflorescence 5–10-flowered, 2–12 mm; petiole (5–)10–30 mm, flat, often narrowly winged. |
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(14) |
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| 14 (13) |
Stamens 3–4 cm, filaments glabrous; abaxial leaf surface glabrous; corolla lobes 2.5–3 cm wide. |
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457 Rhododendron meddianum |
| + |
Stamens 1.8–3 cm, filaments pubescent at base; abaxial leaf surface pubescent along midrib; corolla lobes ca. 2 cm wide. |
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459 Rhododendron eclecteum |
