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Asclepias
See list of 10 species in this genusReference: Woodson (1954).
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1a. Leaves alternate; flowers yellow-orange to orange; latex watery
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1b. Leaves predominantly or entirely opposite or whorled; flowers white to pink, red, purple, or green; latex milky
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2a. Corona with hoods only, the horn lacking [Fig. 365]; umbels sessile or on peduncles up to 1 (–2) cm long
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2b. Corona with horns within the hoods [Figs. 362,363]; umbels borne on peduncles 1–10 cm long [Figs. 361,364]
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3a. Leaf blades narrow-linear, 1–3 (–5) mm wide, in whorls of 3–6 (some scattered) [Fig. 364]
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3b. Leaf blades narrow-lanceolate or narrow-oblong to broad-oblong, broad-elliptic, or ovate, the principal ones 20–140 mm wide, opposite or with 1 or 2 whorls of 4 leaves
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4a. Corona hoods shorter than to ± equaling the height of the gynostegium, with conspicuously exserted horns [Fig. 362]
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5a. Corolla pink to red; corona hoods 2–3 mm long, the lateral margins upwardly divergent (i.e., not parallel), therefore, the hoods scoop-shaped; follicles on erect pedicels; stems branched or, less commonly, simple
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5b. Corolla white, green, green-purple, or pale purple; corona hoods 4–6 mm long, the lateral margins parallel, therefore, the hoods tube-shaped [Fig. 362]; follicles on declined pedicels; stems usually unbranched
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6a. Leaf blades cuneate at base, acuminate at apex, with petioles 10–20 mm long; margins of corona hoods prolonged into a short, erect tooth 1–1.5 mm long; umbels 2–4 from both the stem summit and upper nodes
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4b. Corona hoods taller than the gynostegium, the horns shorter than to equaling the length of the hoods [Fig. 363]
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7a. Corolla white to pink; pedicels 1–2.5 cm long; leaf blades abaxially glabrous or with hairs along the midvein
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8a. Stems with usually 3 or 4 leaf-bearing nodes, the upper and lower nodes with opposite leaves, the middle 1 or 2 nodes with a whorl of 4 leaves (rarely all the leaves opposite); corolla lobes 4.5–6 mm long; lateral margins of corona hoods bearing a tooth near the middle [Fig. 363]; leaf blades gradually acuminate at apex; follicles on erect pedicels
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8b. Stems with 2–5 leaf-bearing nodes, all with opposite leaves; corolla lobes 7–9 mm long; lateral margins of corona hoods without a tooth; leaf blades obtuse to abruptly acuminate at apex; follicles on declined pedicels
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7b. Corolla purple-green to light purple or red-purple to purple; pedicels 2–5 cm long; leaf blades abaxially tomentulose
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9a. Corona hoods 5–7 mm long, red-purple to purple, without marginal lobes; follicles smooth; corolla red-purple to purple
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9b. Corona hoods 4–5 mm long, light purple, each with a prominent marginal lobe near the center; follicles covered with conic processes; corolla purple-green to light purple
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Each photo represents one species in this genus.