| 1 |
Style short, thick, distinctly curved. |
|
(2) |
| + |
Style slender and straight. |
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(8) |
| |
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|
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| 2 (1) |
Stamens 12–16; corolla with wool-like hairs
in the throat. |
|
15 Rhododendron subsect. Camelliiflora |
| + |
Stamens (8–)10; corolla glabrous inside. |
|
(3) |
| |
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|
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| 3 (2) |
Scales strongly dimorphic, the larger dark brown, the smaller golden. |
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16 Rhododendron subsect. Glauca |
| + |
Scales on abaxial leaf surface monomorphic. |
|
(4) |
| |
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| 4 (3) |
Pedicels shorter than corolla; corolla usually yellow, rarely white or pink. |
|
14 Rhododendron subsect. Boothia |
| + |
Pedicels distinctly longer than corolla. |
|
(5) |
| |
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|
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| 5 (4) |
Inflorescences corymbose, 1–3(–5)-flowered; leaves 0.4–2.6(–4) cm. |
|
(6) |
| + |
Inflorescences racemose, 4–10(–18)-flowered; leaves (2–)4–5 cm. |
|
(7) |
| |
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|
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| 6 (5) |
Corolla fleshy, crimson or purple, with scales outside; abaxial leaf surface with distant scales. |
|
17 Rhododendron subsect. Campylogyna |
| + |
Corolla thinner, variable in color, with dense scales outside; abaxial leaf surface with dense scales. |
|
19 Rhododendron subsect. Lepidota |
| |
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|
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| 7 (5) |
Scales entire, small, distant on abaxial surface of leaves; corolla campanulate. |
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18 Rhododendron subsect. Genestieriana |
| + |
Scales crenulate, overlapping on abaxial surface of leaves; corolla rotate. |
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20 Rhododendron subsect. Baileya |
| |
|
|
|
| 8 (1) |
Leaf blade abaxially woolly, hairs obscuring small golden scales. |
|
1 Rhododendron subsect. Edgeworthia |
| + |
Leaf blade abaxially without hairs, or rarely with hairs that do not obscure the scales. |
|
(9) |
| |
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|
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| 9 (8) |
Style with scales, at least at base, sometimes up to tip, rarely without scales; calyx usually conspicuously lobed, occasionally with underdeveloped lobes, then with margin ciliate. |
|
(10) |
| + |
Style entirely without scales; calyx lobes inconspicuous, rarely more than 4 mm. |
|
(11) |
| |
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|
|
| 10 (9) |
Corolla (3–)5–7(–13.5) cm, often white or pink, rarely yellow. |
|
2 Rhododendron subsect. Maddenia |
| + |
Corolla 1.5–3 cm, yellow, white, pink or dark purple. |
|
12 Rhododendron subsect. Tephropepla |
| |
|
|
|
| 11 (9) |
Inflorescences racemose; corolla tubular or campanulate. |
|
(12) |
| + |
Inflorescences corymbose; corolla funnelform or broadly campanulate, rarely tubular-campanulate. |
|
(13) |
| |
|
|
|
| 12 (11) |
Corolla usually pendulous, 2–3.8 cm, often brightly colored, never white, outer surface not lepidote. |
|
11 Rhododendron subsect. Cinnabarina |
| + |
Corolla not pendent, 0.4–1.2 cm, white or yellow, outer surface lepidote. |
|
13 Rhododendron subsect. Micrantha |
| |
|
|
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| 13 (11) |
Corolla thin or fleshy, tubular or narrowly campanulate, lobes short, straight or spreading, though not markedly so. |
|
(14) |
| + |
Corolla thin, funnelform or rotate, lobes spreading. |
|
(15) |
| |
|
|
|
| 14 (13) |
Inflorescences 1–3-flowered; flowers erect; corolla thin, often yellow, outer surface scaly. |
|
4 Rhododendron subsect. Monantha |
| + |
Inflorescences 2–6(–8)-flowered; flowers usually pendulous; corolla fleshy, various in color, sometimes yellow, outer surface not scaly. |
|
11 Rhododendron subsect. Cinnabarina |
| |
|
|
|
| 15 (13) |
Low to tall shrubs, rarely small trees, leaves large, (0.9–)1.3–12 × (0.3–)0.8–3.5(–4) cm. |
|
(16) |
| + |
Low to dwarf shrubs; leaves small to very small, 0.3–4(–7) × 0.15–1.7(–2.8) cm. |
|
(18) |
| |
|
|
|
| 16 (15) |
Inflorescences mostly 5–7(–10)-flowered; corolla always scaly outside. |
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6 Rhododendron subsect. Heliolepida |
| + |
Inflorescences mostly 1–3-flowered, sometimes with 2 or 3 lateral buds below terminal buds; corolla with or without scales outside. |
|
(17) |
| |
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|
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| 17 (16) |
Small shrubs, usually epiphytic; calyx well-developed, lobes red or rosy-purple, rarely green; young shoots usually setose; corolla open-campanulate. |
|
3 Rhododendron subsect. Moupinensia |
| + |
Medium to tall shrubs, rarely small trees, terrestrial; calyx rim-like or shortly lobed; young shoots usually glabrous; corolla broadly funnelform. |
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5 Rhododendron subsect. Triflora |
| |
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|
|
| 18 (15) |
Pedicels 1–5(–15)mm; corolla usually glabrous outside (puberulous in R. dasypetalum). |
|
(19) |
| + |
Pedicels (7–)15–30 mm; corolla pubescent outside. |
|
(20) |
| |
|
|
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| 19 (18) |
Leaf margin entire; scales on abaxial surface flat, with relatively broad rims. |
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7 Rhododendron subsect. Lapponica |
| + |
Leaf margin crenulate; scales on abaxial surface vesicular. |
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9 Rhododendron subsect. Fragariiflora |
| |
|
|
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| 20 (18) |
Abaxial leaf surface with scales dense and overlapping, margin crenulate. |
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8 Rhododendron subsect. Saluenensia |
| + |
Abaxial leaf surface with scales sparser, 0.5–6 times their own diameter apart, margin entire. |
|
10 Rhododendron subsect. Uniflora |
