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Trillium
See list of 6 species in this genusReference: Case and Case (1997).
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1a. Leaf blades usually mottled; flowers sessile; petals erect or arching inward
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1b. Leaf blades not mottled; flowers borne on a peduncle 1–10 cm long; petals either spreading from near the base or flaring outwardly from above the base
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2a. Petals white, with a red-purple crescent-shaped mark near the base; leaves with a short, but distinct, petiole; ovary 3-lobed
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2b. Petals white, pink, or red-purple; leaves sessile (sometimes with an obscure, petiole-like base in T. cernuum); ovary 6-angled or 6-winged (3-lobed in T. nivale)
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3a. Stems at anthesis 3–5 cm tall, elongating to 9 cm post anthesis; leaf blades 1.5–4.5 cm long; peduncles 10–20 mm long
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3b. Stems 10–60 cm tall; leaf blades 5–20 cm long; peduncles (10–) 15–30 mm long
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4a. Petals 4–7.5 cm long, erect in the basal portion and somewhat recurving in the apical portion to produce a funnelform corolla; stigma straight, of uniform diameter throughout its length, usually equaling or exceeding the length of the ovary
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4b. Petals 1.5–5 cm long, spreading or recurved from near the base; stigma conspicuously recurved, tapering in the apical portion, usually half as long as the ovary or shorter
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5a. Petals red-purple (rarely white), 2.5–5 cm long; ovary red-purple to purple; peduncles (1–) 3–8 (–10) cm long, erect to spreading, the flowers only rarely hidden below the leaves
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5b. Petals white, 1.5–2.5 cm long; ovary white to pink; peduncles 1–3 (–5) cm long, recurved, hiding the flowers under the leaves [Fig. 159]
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Each photo represents one species in this genus.