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See list of 8 species in this genus

Tepal measurements for the vining species do not include the narrow, decurrent portion that is adnate to the pedicel. Measurements and shape assessment of the leaf blades for non-vining species should be performed on midbranch leaves, as those near the apex of the branches are not typical (usually both smaller and relatively narrower). References: Kim et al. (2000), Freeman and Hinds (2005).

  • 1a. Stems erect, stout, with hollow internodes; stigmas fimbriate; perianth accrescent
    • 2a. Leaf blades broad-cuneate to truncate at the base, abruptly tapering to the apex, 
5–15 ×2–10 cm, glabrous on the abaxial surface (though usually with blunt scabrules along the major veins) [Fig. 788, R]; midbranch inflorescences about as long as to longer than the subtending leaves
    • 2b. Leaf blades cordate at the base, gradually tapering to the apex, 10–30 ×7–20 cm, sparsely pubescent with long, multicelled hairs on the abaxial surface [Fig. 788, L]; midbranch inflorescences much shorter than the subtending leaves
  • 1b. Stems trailing or climbing, slender, solid; stigmas capitate; perianth usually not accrescent
    • 3a. Stipules reflexed-bristly at the base; stigmas moderately fimbriate
    • 3b. Stipules glabrous; stigmas capitate
      • 4a. Outer 3 tepals merely keeled or with a very narrow wing in fruit; achene striate-papillose, dull except for the lustrous angles [Fig. 787]; plants annual from a wiry taproot
      • 4b. Outer 3 tepals conspicuously winged in fruit; achenes smooth, lustrous [Fig. 789]; plants perennial from a rootstock or annual from a taproot
        • 5a. Plants woody near the base (i.e., lianas); flowers white, borne in profuse, branched panicle-like inflorescences; axis of inflorescence brown-white to very 
pale brown; bracteoles subtending the pedicels (i.e., ocreolae) cream-colored, caudate-tipped
        • 5b. Plants herbaceous throughout (i.e., vines); flowers green to green-white (infrequently brown-green or tinged with red), borne in raceme-like inflorescences or small, axillary fascicles; axis of inflorescence green or red (rarely pale); bracteoles subtending the pedicels green to brown, truncate or oblique at apex
          • 6a. Fruiting tepals 3.4–5.1 mm long, with crenate or irregularly jagged and often crisped wings, the wings green to green-white, relatively poorly developed especially near the apex and only 0.25–1 mm wide; achenes 2.4–2.9 mm long
          • 6b. Fruiting tepals 4.2–9.4 mm long, with entire to weakly undulate and plane wings, the wings cream to pale brown or tinged with red, well-developed even near the apex and 1–3 mm wide (rarely poorly developed in F. dumetorum); achenes 2.8–5.1 mm long
            • 7a. Fruiting tepals 4.2–6.5 (–7) mm long, often abruptly contracted near the base and only shortly decurrent on the pedicel; achenes 2.8–3.5 (–3.7) mm long; perianth suborbicular to broad-oval or broad-oblong in side view; basal lobes of leaf blades mostly 3–8 mm long when measured parallel to petiole
            • 7b. Fruiting tepals (6.2–) 6.5–9.4 mm long, usually gradually narrowed and long-decurrent on the pedicel; achenes (3.5–) 3.7–5.1 mm long; perianth oval to oval-obovate or narrow-obovate in side view; basal lobes of leaf blades mostly 9–19 mm long when measured parallel to the petiole

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