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Published In: Systema Vegetabilium 2: 154. 1817. (Syst. Veg. (ed. 15 bis)) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 9/1/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native


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1. Eleocharis acicularis (L.) Roem. & Schult. (slender spike rush, least spike rush)

Pl. 74 i, j; Map 274

E. acicularis f. fluitans (Döll ex Glück) Svenson

E. acicularis f. longicaulis (Desm.) Hegi

E. acicularis var. gracilescens Svenson

Plants perennial, appearing tufted, often forming mats, the tufts connected by slender, hairlike rhizomes (actually stolons). Aerial stems 2–20(–40) cm long, 0.2–0.5 mm in diameter, 4–5-angled in cross-section and usually finely ridged, lacking cross-lines. Basal sheaths loose, reddish tinged toward the base, the tip membranous, truncate or slightly oblique. Spikelets 2–6(–12) mm long, ovate-lanceolate to linear in outline, pointed at the tip, with 1 sterile, basal scale. Scales 1.5–2.2 mm long, ovate-lanceolate, pointed at the tip, with a green central area, a reddish brown area on each side, and usually white-membranous margins. Perianth bristles lacking or 3–4, slender, about as long as or somewhat shorter than the fruits, usually not barbed. Stigmas 3. Fruits 0.7–1.0 mm long, the main body elliptic-obovate in outline, slightly 3-angled to nearly circular in cross-section, the surface with mostly 10–18 longitudinal ridges with numerous fine cross-lines between them, white (rarely pale gray or light tan), shiny. Tubercles short, narrowly conical-triangular. 2n=20, 30–38, 50–58. July–October.

Scattered nearly throughout Missouri, commonest in the Ozarks (North America south to northern Mexico, Europe, Asia). Margins of ponds, lakes, sloughs, springs, and ditches, often colonizing receding shorelines.

Mats of this species can grow so densely as to inhibit the establishment of other aquatic species, and E. acicularis has sometimes been seeded into small farm ponds to keep them from becoming choked out with other, more robust aquatic plants. Although the species often occurs along receding shorelines, it also grows well submerged. Such plants sometimes have longer stems (to 40 cm long) and larger spikelets (6–12 mm long). These ecotypes have been referred to as var. gracilescens and f. longicaulis (Desm.) Hegi.



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