Carex sect. Bicolores
Fl. France 13: 508. 1912.
Plants loosely cespitose, rhizomatous. Culms brown at base. Leaves: basal sheaths not fibrous; sheath fronts membranous; blades V-shaped in cross section when young, glabrous. Inflorescences racemose, with 2–6 spikes, rachis of spikes papillose; bracts usually leaflike, rarely scalelike, sheathing or sheathless; lateral spikes pistillate, sometimes the proximal, pedunculate, prophyllate, not much longer than wide; terminal spike staminate or gynecandrous. Proximal pistillate scales with apex obtuse to acuminate. Perigynia ascending to spreading, weakly veined, stipitate, sometimes inflated, elliptic-obovate, biconvex to subcircular in cross section, base tapering to rounded, margins rounded, apex rounded, beakless or short-beaked, glabrous, sometimes papillose; beak orifice entire. Stigmas 2. Achenes biconvex, smaller than bodies of perigynia; style deciduous.
Temperate and low arctic regions of the Northern Hemisphere.
Species 4 (4 in the flora).
Carex sect. Bicolores is a small apparently natural section of uncertain relationships. The species are superficially very different, which has led some authors to allocate them to different sections. Carex aurea was included in sect. Paniceae by G. Kükenthal (1909); C. bicolor was placed in sect. Phacocystis. T. V. Egorova (1999) and A. O. Chater (1980) placed C. bicolor in sect. Atratae. The four species form a morphologic continuum with only weak discontinuities. Putative hybrids between the species appear to be fertile and can be difficult to recognise. Intersectional hybrids involving member of sect. Bicolres are uncommon. The sterile hybrid, C. garberi × C. tetanica (sect. Paniceae), occurs occasionally in meadows and shoreline fens where the two parent species grow together. K. K. Mackenzie (1931–1935, parts 2–3, pp. 230–234) included a fifth species, C. rufina Drejer, in the section. Carex rufina has a more distinct perigynium beak and a setose-serrulate distal margins of the perigynium. It is here included in sect. Phacocystis.
|1||Lateral spikes lax, middle internodes (0.5–)0.7–1.5 mm; terminal spike usually staminate.||> 2|
|1||Lateral spikes dense, middle internodes 0.2–0.7 mm; terminal spike usually gynecandrous.||> 3|
|2||Terminal spike 0.9–2 mm wide; proximal staminate scales 2–3.5(–4) mm; perigynia bright orange when mature, divergent; pistillate scales divergent in mature fruit.||Carex aurea|
|2||Terminal spike (1.8–)2–3.5 mm wide; proximal staminate scales 3–6(–15) mm; perygynia whitish when mature, ascending; pistillate scales ascending.||Carex hassei|
|3||Terminal spike with usually not more than 1/3 of total number of flowers staminate, staminate portion 1.1–1.8 mm wide; pistillate scales usually black with green midvein, rarely dark brown.||Carex bicolor|
|3||Terminal spike with more than 1/3 of total number of flowers staminate, staminate portion (1.2–)1.5–3.5 mm wide; pistillate scales pale to dark brown.||> 4|
|4||Proximal staminate scales (2–)2.5–3.7 mm, apex obtuse to acute; pistillate scales medium to dark brown, apex obtuse to acute or very shortly mucronate.||Carex garberi|
|4||Proximal staminate scales 3–6(–15) mm, apex often long-acuminate; pistillate scales pale to medium brown, apex often mucronate or aristate.||Carex hassei|