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Published In: Familles des Plantes 2: 495. 1763. (Fam. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

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


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21. Apera Adans. (silky bent grass)

Plants annual, forming tufts. Flowering stems erect, sometimes from spreading bases, glabrous, darkened at the nodes. Leaf sheaths rounded on the back to slightly keeled, glabrous, the ligule 0.5–3.0 mm long, often somewhat torn or irregularly lobed or toothed. Leaf blades flat or with inrolled margins, glabrous or more commonly roughened. Inflorescences open to dense panicles with strongly ascending to spreading branches, erect. Spikelets slightly flattened laterally, disarticulating above the glumes, with 1 perfect floret and without additional staminate or sterile florets. Glumes rounded or somewhat keeled, lanceolate, narrowed to a sharply pointed tip, awnless, roughened on the midnerve, unequal in length, the lower glume shorter than the floret, 1‑nerved, the upper glume slightly longer than the floret, 3‑nerved. Lemma not membranous at maturity, lanceolate, sharply pointed at the tip, rounded on the back, faintly 5‑nerved, roughened toward the tip, the base with a tuft of very short, straight hairs, with a well‑developed awn 4–12 mm long (longer than the spikelet) attached just below the tip. Palea slightly shorter than the lemma, membranous, 2‑nerved. Stamens 3. Fruits 1.2–1.6 mm long, narrowly oblong‑elliptic in outline, yellowish brown. Three or 4 species, Europe, Asia; introduced in North America.

Apera was included in the genus Agrostis by many earlier authors of American floras (Steyermark, 1963), but it is distinct from that genus by virtue of its spikelets with a well‑developed palea, a long‑awned, relatively firm lemma, and unequal glumes (McNeill, 1981). These characters appear occasionally in various species of Agrostis but are uncommon and do not occur in tandem in that genus. Care must be taken not to confuse species of Apera with the superficially similar Agrostis gigantea and A. stolonifera.


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1 Leaf blades 1–4 mm wide, usually with strongly inrolled margins; inflorescences relatively narrow, with strongly ascending branches at maturity; upper glume 2.0–2.5 mm long 1 Apera interrupta
+ Leaf blades 3–10 mm wide, usually flat; inflorescences open panicles, the branches loosely ascending to spreading at maturity; upper glume 2.4–3.2 mm long 2 Apera spica-venti
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