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Bolboschoenus

Anther color, scale translucence, and anatomy of the achenes are critically important for identification of Bolboschoenus specimens. Anther color should be assessed on dried specimens (or dehisced anthers on living plants). Scale translucence is best viewed under a dissecting scope at 10–15 power. Placing a narrow probe or similar tool under the floral scale with good lighting is a good method of assessing how much light passes through the scale (based on how readily the probe can be viewed through the scale). Achene anatomy is viewed in cross-section (i.e., the achenes need to be cut in half with a sharp blade). Hybrids are relatively common and can form large colonies. They generally show decreased fertility and produce fewer well-formed achenes. References: Browning et al. (1995), Smith (2002a).

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1a. Inflorescence normally with elongate branches; styles mostly trifid; achenes  compressed-trigonous to equilaterally trigonous; perianth bristles present on mature  achenes [Fig. 66], sometimes a few caducous; achene exocarp layer 0.15–0.5 times  as deep as the mesocarp layer; plants of fresh to slightly brackish shores
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  B. glaucus
  2a. Widest leaf blades 2–6 mm wide; spikes slender, mostly 3–5 mm in diameter; achenes 2.5–3.3 mm long, with a minute, persistent style beak; veins of leaf sheaths gradually diverging near summit, leaving an obtriangular, veinless area
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  2b. Widest leaf blades 7–22 mm wide; spikes thicker, mostly 5–10 mm in diameter; achenes 3–5.5 mm long, with an evident style beak 0.1–0.8 mm long [Fig. 66]; veins of leaf sheaths nearly reaching summit before abruptly diverging
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    B. fluviatilis
    3a. Achenes 3.8–5.5 mm long, usually equilaterally trigonous, with isodiametric exocarp cells; perianth bristles firmly attached to achene, equaling the length of the achene [Fig. 66]; anthers yellow
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    B. novae-angliae
    3b. Achenes 3–4.3 mm long, usually compressed-trigonous, with exocarp cells 1.5–3 times as tall as wide; perianth bristles weakly attached to achene, 0.5–1 times the length of the achene; anthers dark yellow to orange-yellow
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1b. Inflorescence normally congested and lacking elongate branches; styles bifid or trifid; achenes plano-convex to compressed-trigonous; perianth bristles rarely present on mature achenes; achene exocarp layer ± 2 times as deep as the mesocarp layer; plants of saline to brackish shores
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  B. robustus
  4a. Floral scales opaque, papery-textured, with awns ca. 0.5 mm wide at the base; anthers yellow when fresh, becoming orange-brown to red-brown after dehiscence or in drying; achenes dark brown, often compressed-trigonous; apex of leaf sheath opposite the leaf blade with abruptly diverging veins, green and firm-textured, prolonged
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  B. maritimus
  4b. Floral scales translucent, membranous-textured, with awns ca. 0.25 mm wide at the base; anthers yellow when fresh, becoming pale yellow or pale yellow-brown after dehiscence or in drying; achenes light brown to dark brown, lenticular or rarely compressed-trigonous; apex of leaf sheath opposite the leaf blade with gradually diverging veins, with a hyaline obtriangular area, not prolonged

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