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Cyperaceae
See list of 17 genera in this family-
1a. Perianth at maturity composed of elongate capillary bristles that greatly exceed the subtending floral scales, creating a “woolly” or “cottony” appearance to the individual spikes [Fig. 120]
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2a. Perianth bristles strongly bent, curled, and tangled; inflorescences with 50–500 spikes (in part)
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2b. Perianth bristles relatively straight, silky; inflorescences with 1–10 (–30) spikelets
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3a. Perianth bristles numbering 10–25 per flower; spikelets solitary or 2–10 (–30) per inflorescence, 10–50 mm long in fruit, subtended by 1 or more foliaceous bracts or by 10–15 sterile, basal scales; principal leaf blades up to 45 cm long
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3b. Perianth bristles mostly 6 in each flower; spikelets solitary, 5.4–8 mm tall in fruit, subtended by a solitary involucral bract that resembles an enlarged, basal scale; leaf blades up to 1 cm long (in part)
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1b. Perianth absent or present, when present not composed of greatly elongated capillary bristles, mostly contained within the floral scales [Figs. 68,73,110]
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4b. Carpellate flowers subtended by flat or folded scales, never enclosed in a sac-like scale [Figs. 105,110,125]; flowers bisexual or some unisexual (all unisexual in Scleria), with or without perianth
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5a. Spikes 1 per stem
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6a. Involucral bract solitary, erect, appearing to be a continuation of the stem, therefore, the inflorescence falsely appearing to emerge from the side of the stem; leaf blades flaccid, submerged or the tips floating (in part)
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6b. Involucral bracts (if present) not resembling a continuation of the stem, therefore, the inflorescence appearing terminal; leaf blades either not produced or firm
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7b. Achenes not crowned by a tubercle; at least the upper leaf sheaths blade-bearing (in part)
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5b. Spikes usually 2 or more per stem
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8a. Scales of spikes distichous (i.e., arranged in 2 ranks) [Fig. 105]
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9a. Inflorescence partly or wholly axillary; flowers with a perianth composed of bristles; style persistent on the achene as a slender beak; leaves borne on the stem
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9b. Inflorescence terminal; flowers lacking perianth; style deciduous from the achene; leaves basally disposed
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10b. Spikelets with 2 (rarely 3) subopposite floral scales, the basal scale subtending a bisexual flower, the apical scale subtending a staminate flower; inflorescence densely capitate, with sessile spikes; achenes biconvex, the edge not fitting into a groove in the rachilla
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8b. Scales of spikes spirally arranged (i.e., arranged in 3 or more ranks)
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11a. Flowers all unisexual; achenes white, gray, or gray-brown, with a hardened disk at the base (i.e., a hypogynium; the hypogynium vestigial in S. verticillata)
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11b. Flowers bisexual or some unisexual; achenes mostly gray-brown or pale brown to dark brown or black, without a hypogynium
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12a. Principal involucral bract solitary, erect, appearing to be a continuation of the stem, therefore, the inflorescence falsely appearing to emerge from the side of the stem
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13a. Achenes 0.5–0.7 mm long; spikelets 1–3 (–5) mm long; perianth consisting of a single, diminutive scale; floral scales 0.5–1 mm long
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13b. Achenes 1.3–4 mm long; spikelets 5–15 mm long; perianth consisting of bristles [Fig. 126], these sometimes caducous; floral scales 2–6 mm long (in part)
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12b. Principal involucral bract erect to spreading, flat, folded, or setaceous, accompanied by additional bracts, not seeming a continuation of the stem, the inflorescence appearing terminal
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15a. Perianth dimorphic––an outer set of 3 retrorse-barbellate bristles and an inner set of 3 stipitate blades terminating in acuminate or awned apices [Fig. 121]; leaf sheaths pubescent
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15b. Perianth monomorphic, of smooth to retrorse-barbellate bristles, or absent [Fig. 66]; leaf sheaths glabrous
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16a. Plants annual, with soft stem bases and fibrous roots, 5–30 cm tall
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17a. Stems capillary; leaves up to 0.5 mm wide, with two lateral tufts of hairs at the junction of the blade and sheath; style base persistent in fruit and forming a tiny tubercle
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17b. Stems flat; larger leaves 1–3 mm wide, none with two lateral tufts, but with a ligule of short hairs; style base not persistent in fruit
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16b. Plants perennial, with hardened stem bases and rhizomes, 30–200 cm tall
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18a. Perianth absent; achenes terete in cross-section; each spike with 1–3 empty, basal scales and an apical, bisexual flower, the remaining scales subtending staminate flowers
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18b. Perianth usually present, caducous in some species (rarely absent); achenes lenticular or biconvex to trigonous in cross-section; spikes comprised entirely of bisexual flowers
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19a. Scales pubescent on the abaxial surface; rhizomes with tuberous thickenings; spikes (7–) 10–40 mm long; achenes 2.3–5.5 mm long; leaves without ligules
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19b. Scales glabrous on the abaxial surface; rhizomes without tubers; spikes 2–12 mm long; achenes 0.6–1.6 mm long; leaves with ligules (in part)
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Each photo represents one genus in this family.