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bulbostyle, hairsedge

Habit Herbs, annual or perennial, cespitose, scapose, not rhizomatous.
Roots

diffuse, very fine.

Culms

stiff or flaccid, usually terete, ribbed.

Leaves

basal, polystichous, spreading to ascending;

sheaths open apically, apex fimbriate-ciliate, rarely entire;

ligules absent, lateral tufts of hair at junction of blade and sheath;

blades mostly linear or filiform, coarsely ribbed, usually longer than sheaths, 1 mm wide or less, mostly strongly involute, margins variably scabrid-ciliate.

Inflorescences

terminal on slender scapes, rarely axillary to culm leaves, simple or compound anthelae or spikelet solitary;

spikelets 1–50+;

involucral bracts (1–)2–8, spreading or erect, leaflike or scalelike.

Spikelets

mostly ovoid to lanceoloid or lance-cylindric;

scales 6–50, spirally arranged, rarely nearly distichous, each subtending flower or 1–2 proximal scales empty.

Flowers

bisexual;

perianth absent;

stamens 1–3;

styles slender, (2–)3-fid, glabrous, base enlarged, persistent in fruit.

Achenes

trigonous or 3-lobed, rarely biconvex, usually 3-ribbed.

Bulbostylis

Distribution
from USDA
Mostly of dry or periodically dry; sunny; sandy uplands; particularly savanna in warm-temperate and tropical regions worldwide
[BONAP county map]
Discussion

Species ca. 100 (8 in the flora).

Culms of bulbostylises are coarse or fine, leafy only at the base, and terminating in scape (or rarely not scapose). Scapes are linear to filiform, wiry, variously ribbed. Spikelets or florets are short-stalked, even sessile in leaf axils. Flowers are protandrous and subsessile on short pedicellar joints; anthers are mostly linear-oblong or oblong-elliptic, two- to four-sporangiate, bilocular; style base is articulated to ovary summit and persists on fruit as buttonlike tubercle.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Spikelets sessile or subsessile, forming globose to hemispheric head, head subtended by setaceous-tipped or cuspidate involucral bracts.
→ 2
1. Spikelets either solitary at culm tip or in anthelae, sometimes short-stalked (B. capillares), at plant base in leaf axils.
→ 4
2. Achene faces finely reticulate, not transversely rugose or rugulose; achenes 0.5–0.6 mm; spikelets red, red-brown, or dull brown; longer involucral bracts rarely exceeding inflorescence.
B. barbata
2. Achene faces transversely rugose or rugulose; achenes 1–1.2 mm; spikelets pale or greenish or tan; longer involucral bracts exceeding inflorescence.
→ 3
3. Involucral bracts with broad, scarious, strongly pectinate-fimbriate sheath border abruptly narrowing to blade; plants perennial, to 50 cm; anthers 3, 3 mm.
B. warei
3. Involucral bracts with scarious, entire border gradually narrowing to blade; plants annual, to 20 cm; anthers 1, 0.5 mm.
B. stenophylla
4. Spikelets 1 per culm; plants diminutive, delicate annuals.
→ 5
4. Spikelets prevalently more than 1 per culm, in anthelae; plants tall annuals or perennials.
→ 6
5. Spikelets of 2 sorts, sterile and fertile, respectively producing non-viable achenes, 1 mm or less, or viable achenes, 1.5 mm, in sheath axils at culm base.
B. funckii
5. Spikelets fertile, achenes all viable, 1 mm.
B. schaffneri
6. Surface of ripe achenes waxy gray, evenly papillate; Coastal Plain of United States.
B. ciliatifolia
6. Surface of ripe achenes pale red-brown, greenish or yellow-brown, tan, or gray, minute alveolae or papillae raised into finely or coarsely transversely rugose or rugulose faces; wider distribution.
→ 7
7. Plants hard-based, perennial; achene surfaces gray, yellow-brown or dark brown, rugulose, papillate; stamens 3; anthers 1 mm.
B. juncoides
7. Plants soft-based, annual; achene surfaces mostly yellow to pale brown, rugose, not papillate; stamens (1–)2; anthers 0.5–0.7 mm.
B. capillaris
Source FNA vol. 23, p. 131. Author: Robert Kral.
Parent taxa Cyperaceae
Subordinate taxa
B. barbata, B. capillaris, B. ciliatifolia, B. funckii, B. juncoides, B. schaffneri, B. stenophylla, B. warei
Synonyms Oncostylis, Stenophyllus
Name authority Kunth: Enum. Pl. 2: 205. 1837, name conserved, not Steven 1817 or de Candolle (1836)
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