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Key to Cuscuta

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1 Styles united for most of their length; capsule circumscissile; [subgenus {or genus} Monogynella].
  2 Stigmas flattened-depressed; corollas 2.5-4 mm long
  2 Stigmas conic, ellipsoid, globose, obovoid, ovoid, or cuboid; corollas 3-7 mm long.
    3 Corollas 4-7 mm long; stigmas cuboid
1 Styles separate and distinct from the base; capsule not circumscissile (except the rare exotics C. epilinum and C. epithymum).
      4 Stigmas elongated, terete or conical; capsule circumscissile; [subgenus {or genus} Cuscuta].
        5 Style about equaling the ovary, included in the corolla; fruit 2.0-2.5 mm long
        5 Style (including the stigma) much longer than the ovary, exserted from the corolla; fruit ca. 1.5 mm long
      4 Stigmas capitate, about as wide as long; capsule not circumscissile, either indehiscent or rupturing irregularly; [subgenus {or genus} Grammica].
          6 Each flower subtended by 1-10 imbricate bracts; sepals distinct nearly to the base.
               8 Pedicels absent, the flowers in compact clusters sessile on the stem; bracts tightly subtending the flower, orbicular with rounded apices; styles not exserted in flower, and only 1.5-1.8 mm long in fruit; corolla lobes 0.9-1.1 mm long
               8 Pedicels 0.5-3 mm long, the flowers in loose panicles; bracts loosely subtending the flower, ovate with bluntly pointed apices; styles long-exserted, 2.5-3.5 mm long in flower and fruit; corolla lobes 1.8-2.0 mm long
          6 Flowers not bracteate (rarely a single bract may be present towards the base of the pedicel); sepals various.
                 9 Perianth surface granular (papillate); fresh flowers fleshy; corolla lobes acute, tips typically curved inward.
                   10 Corolla tubular; calyx > ½ as long as the corolla; flowers 4 (-5)-merous; infrastaminal scales reduced, merely bifid or shallowly toothed
                     11 Calyces shorter than the corolla tubes, divided 1/3-1/2 of the lengths; calyx lobes triangular-ovate, bases overlapping
                     11 Calyces longer than the corolla tubes, divided 2/3 of the lengths; calyx lobes lanceolate, the lobes not overlapping.
                       12 Flower clusters dense; calyx lobes acute-attenuate; hosts usually Iva annua, more rarely Symphyotrichum
                 9 Perianth surface not granular; fresh flowers not especially fleshy; corolla lobes various.
                          13 Stylopodium (a thickened ridge at the base of the style) present; flowers 5-merous.
                            14 Ovary with a long (1-1.5 mm), beak-like projection at the top; corolla 4-6 mm long, 4-6 mm wide; seeds 2-3 mm long; [of the Mountains]
                            14 Ovary blunt to pointed, but not beaked; corolla 2.2-3.5 mm long, 2-3 mm wide; seeds ca. 1.5 mm long; [widespread].
                              15 Flowers 2.3-3.1 mm long; calyx ca. as long as the corolla tube or slightly shorter, lobes oblong-ovate, not overlapping basally; corolla 2.2-2.7 (-3) mm long, tube 0.8-1.5 (-2) mm long, broadly campanulate to cupulate; infrastaminal scales longer than the corolla tube; capsules surrounded by the withered corolla in the lower 1/2
                              15 Flowers 3-4.5 mm long; calyx ca. reaching the middle of the corolla tube, lobes ovate to suborbicular, basally overlapping; corolla 3-4.4 mm long, tube (1.7-) 2-2.5 (-2.8) mm long, campanulate, infrastaminal scales shorter than the corolla tube to nearly reaching filament bases; capsules 3/4 surrounded by the withered corolla or capped in the distal 1/2 by it.
                                16 Infrastaminal scales ca. reaching filament bases (rarely shorter), apex rounded; styles (0.6-) 1.1-2.5 mm long
                                    18 Flowers on pedicels slightly shorter than to longer than the flowers, therefore in loose inflorescences.
                                             22 Flowers 1.5-3.0 mm long, at least some exceeding 2.5 mm long; calyx lobes not overlapping at the base in older flowers, and therefore the flowers not pronouncedly 5-angled
                                             22 Flowers 0.9-2.5 mm long; calyx lobes strongly overlapping and forming definite angles at the sinuses, thus the flower strongly 4-5-angled.
                                               23 Flowers 4-merous; flowers 0.9-1.4 mm long; stems very slender; [on granite and sandstone outcrops]
                                               23 Flowers 5-merous; flowers 1.5-2.5 mm long; stems not especially slender; [widespread]
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