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Sagittaria
See list of 9 species in this genusFruits must be mature to show features such as facial wings, facial glands, and beak orientation. Width of the leaf at its midpoint is used in the following key—the measurement should not be taken at the midpoint of the leaf blade but at the midpoint of the leaf; i.e., combined length of the petiole and blade (when a blade is present).
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1a. Sepals of carpellate flowers appressed in fruit [Fig. 59]; pedicels recurved (rarely spreading) in fruit [Fig. 59]
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2a. Lower flowers bisexual; leaves represented by thick, spongy phyllodia (2–) 2.5–8 (–8.5) mm wide at the midpoint in drying (sometimes with a small, expanded blade at the apex)
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2b. Lower flowers carpellate; leaves represented by phyllodia that are flattened or lenticular in cross-section and 0.7–2.7 mm wide at the midpoint in drying (sometimes with a small, expanded blade at the apex)
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3a. Leaves 5–30 cm long; peduncles 5–40 cm long; plants predominantly of brackish, tidal shores
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3b. Leaves 30–90 (–250) cm long; peduncles 10–200 cm long; plants predominantly of fresh, moderately moving rivers
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1b. Sepals reflexed in fruit; pedicels ascending to spreading in fruit
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4a. Filaments smooth [Fig. 58]; leaves usually with blades that possess basal lobes
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5a. Bracts of inflorescence thick and herbaceous, distinct or with margins connate less than 25% of their total length; achenes with 1–3 facial wings; inflorescence with 2–4 whorls of pedicels
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5b. Bracts of inflorescence thin and scarious, with margins connate 25% or more of their total length; achenes with 0 or 1 facial wings; inflorescence with 2–10 whorls of pedicels
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6a. Beak of the achene 0.1–0.5 mm long, erect; petals 7–10 mm long; achenes 1.8–2.6 mm long; floating leaves with sagittate-ovate blades produced on some deep-water plants; emersed leaves with a broad-lanceolate to triangular-ovate central lobe and borne on recurving petioles
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6b. Beak of the achene 0.6–1.8 mm long, horizontally spreading; petals 10–20 mm long; achenes 2.5–4 mm long; floating leaves with expanded blades not produced; emersed leaves with highly variable blades, the central lobe ranging from linear to broad-ovate, borne on ascending petioles
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4b. Filaments rough, beset with minute hairs [Fig. 57]; leaves either without blades or with blades that usually lack basal lobes
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7a. Leaves all phyllodial, elliptic to terete in cross-section, generally tapering from near the base to the apex
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7b. Leaves phyllodial and with ± parallel margins that taper somewhat abruptly to the apex or with an expanded blade, in either case flattened
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8a. Lowest whorl of carpellate flowers borne on pedicels 1–3 cm long; flowering stem straight, without a distinct bend; achenes 1.5–2 (–2.8) mm long, with a short beak 0.1–0.3 mm long; leaf blades (when formed) narrow-lanceolate to broad-lanceolate
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8b. Lowest whorl of carpellate flowers sessile or on short pedicels up to 0.5 cm long; flowering stem often with a conspicuous bend at the lowest whorl of flowers; achenes 2.5–4 mm long, with a beak 0.8–1.4 mm long; leaf blades (when formed) lanceolate to oblong-ovate or elliptic-ovate
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Each photo represents one species in this genus.