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Section Acrocystis
See list of 11 species in this sectionHybrids between a species that lacks basal spikes (e.g., Carex pensylvanica) and a species that possesses basal spikes (e.g., C. tonsa, C. umbellata) have been observed in New England. They are difficult to confidently identify and are suspected to be sterile. They typically have the basal spikes of one parent but otherwise resemble the other parent. Reference: Crins and Rettig (2002).
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1a. All the carpellate spikes of a plant borne well above the base in proximity to a staminate spike on stems with leaf bearing nodes
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2a. Perigynium body (i.e., excluding the beak and stipe-like base) subglobose, about as wide as long as thick
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3a. Widest leaf blades (2.6–) 3–5 mm wide; plants cespitose, with short rhizomes; remnants of old leaves not or only slightly fibrous; staminate spikes 1–2.5 mm wide
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3b. Leaf blades 0.5–3 (–3.6) mm wide; plants extensively colonial, with long rhizomes; remnants of old leaves slightly to strongly fibrous; staminate spikes (1.3–) 2–4.6 mm wide
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4a. Perigynia with a beak 0.5–0.9 mm long and 0.1–0.5 times as long as the body of the perigynium; uppermost stem leaves with a well-developed blade; apical portion of the sheath opposite the leaf blade shallowly concave, the cleft extending 0.2–1.6 mm below the junction with the leaf blade
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4b. Perigynia with a beak 0.9–1.6 mm long and 0.5–1 times as long as the body of the perigynium [Fig. 67]; uppermost stem leaves with a poorly developed blade; apical portion of the sheath opposite the leaf blade deeply concave, the cleft extending 0.4–6.9 mm below the junction with the leaf blade
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2b. Perigynium body ellipsoid to obovoid, definitely longer than thick
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5a. Lowest carpellate spike short-pedunculate, separated from the upper spikes by a gap of more than 7 mm; lowest bract of inflorescence usually equaling or exceeding total height of inflorescence
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5b. Lowest carpellate spike sessile, approximate to or overlapping the upper spikes, usually with a gap of less than 7 mm from the upper spikes; lowest bract of inflorescence usually shorter than total height of inflorescence (except in C. deflexa and C. reznicekii)
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6a. Carpellate scales ½ to ⅔
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7a. Reproductive stems 5–31 cm tall, usually equaled or exceeded by the leaves; perigynia 2.3–3.1 mm long (in part)
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7b. Reproductive stems 21–47 cm tall, usually exceeding the leaves; perigynia 3.2–4.2 mm long
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6b. Carpellate scales equaling to slightly exceeding the perigynia, therefore, the perigynia largely concealed within the intact spikes
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8a. Peduncle of staminate spike 0.4–9.9 mm long; remnants of old leaves slightly or not at all fibrous; reproductive stems (10–) 20–45 cm tall; achenes 1.2–1.4 (–1.7) mm long; perigynia 2.3–3.3 mm long
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8b. Peduncle of staminate spike (0.2–) 0.3–1.2 mm long; remnants of old leaves slightly to strongly fibrous; reproductive stems 1.9–20 (–27) cm tall; achenes 1.4–2 mm long; perigynia (2.5–) 2.8–3.7 (–3.9) mm long
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9a. Widest leaf blades (1.9–) 2.3–4.5 mm wide; carpellate scales sometimes with anthocyanic pigment extending from near the margin to the green or brown stripes on either side of the midvein; reproductive stems 8–38 cm tall; longest staminate spike exceeding the carpellate spikes by (0–) 0.5–5.1 (–7.3) mm
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9b. Widest leaf blades 1.2–2.2 (–2.5) mm wide; carpellate scales never with anthocyanic pigment extending from near the margin to the green or brown stripes on either side of the midvein; reproductive stems 1.9–9.1 (–13.7) cm tall; longest staminate spike exceeding the carpellate spikes by 0–3.7 mm
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1b. Some of the carpellate spikes solitary and borne on leafless peduncles originating from the plant base without associated staminate spikes (the solitary carpellate spikes sometimes hidden among the leaf bases), the other carpellate spikes borne on leaf-bearing stems with a staminate spike [Fig. 68]
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10a. Carpellate scales ½ to ⅔ as long as the perigynia they subtend, therefore, the perigynia clearly visible within the intact spikes; remnants of old leaves slightly or not at all fibrous; lowermost bract of inflorescence usually equaling or exceeding total height of inflorescence (in part)
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10b. Carpellate scales equaling to slightly exceeding the perigynia, therefore, the perigynia largely concealed within the intact spikes; remnants of old leaves weakly to strongly fibrous; lowermost bract of inflorescence usually shorter than total height of inflorescence
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11a. Perigynium 3.1–4.7 mm long, with a beak 0.9–2 mm long; leaf blades coriaceous or herbaceous
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11b. Perigynium 2.2–3.2 mm long, with a beak 0.4–1 mm long [Fig. 69]; leaf blades herbaceous
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Each photo represents one species in this section.