Minuartia muscorum
Minuartia obtusiloba
Dixie stitchwort, starwort
alpine sandwort, alpine stitchwort, arctic sandwort, twin-flower sandwort
filiform.
stout, woody.
erect, green, 10–55 cm, glabrous or weakly stipitate-glandular distally, internodes of all stems 0.5–2.5 times as long as leaves; wintering stems absent.
erect, green, 1–12 cm, trailing stems 2–20+ cm, stipitate-glandular, internodes of flowering stems 1–6 times as long as leaves.
not overlapping, connate proximally, with loose, scarious sheath 0.4–0.8 mm;
blade straight to variously curved, green, flat, 1-veined, linear-lanceolate to oblanceolate, (5–)10–35(–50) × (0.6–)1.5–3.2 mm, flexuous, margins not thickened, herbaceous or thinly scarious, smooth, apex green, acute, flat, dull, glabrous;
axillary leaves absent.
tightly overlapping (vegetative), variably spaced (cauline), usually connate proximally, with tight, scarious to herbaceous sheath 0.3–1.5 mm;
blade straight to outwardly curved, green, 3-angled, 3-veined abaxially, midrib prominent, lateral veins weak in distal 1/3, needlelike to subulate, 1–8 × 0.4–1 mm, flexuous, margins not thickened, herbaceous, sometimes finely ciliate, apex green, rounded to acute, often apiculate, somewhat navicular, shiny, glabrous;
axillary leaves present among vegetative leaves.
5–50+-flowered, open cymes;
bracts lanceolate to subulate, herbaceous.
solitary flowers, terminal, or occasionally in 2–3-flowered, open cymes;
bracts subulate, herbaceous.
0.6–5.5 cm, stipitate-glandular.
0.3–1.5 cm, stipitate-glandular.
hypanthium shallowly disc-shaped;
sepals prominently 3-veined, lanceolate (herbaceous portion narrowly lanceolate), 3–4 mm, to 5 mm in fruit, apex green, acute, not hooded, stipitate-glandular;
petals obovate, 1.6–3 times as long as sepals, apex rounded, broadly notched.
hypanthium cup-shaped;
sepals prominently 3-veined proximally, narrowly ovate to oblong (herbaceous portion lanceolate to oblong), 2.9–6.5 mm, not enlarging in fruit, apex often purple, narrowly rounded, hooded;
petals ovate to spatulate, 1.2–2 times as long as sepals, apex rounded, entire.
on stipe ca. 0.1 mm or shorter, ovoid to broadly so, 5.2–7 mm, longer than sepals.
narrowly ellipsoid, 3.5–6 mm, equaling sepals.
black, suborbiculate, radicle obscure, plump to slightly compressed, 0.6–0.8 mm, muriculate-papillate.
reddish tan, suborbiculate with radicle prolonged into beak, somewhat compressed, 0.6–0.7 mm, obscurely sculptured (50x).
= 26, ca. 52, 78.
Minuartia muscorum
Minuartia obtusiloba
Minuartia muscorum is closely related to M. patula, and is distinguished by the often longer and wider leaves, often longer distal stem internodes, consistently three-veined sepals, and shiny, black, muriculate-papillate seeds. B. Maguire (1951) treated this taxon as both a variety of Arenaria patula and a new species; see R. K. Rabeler (1992) for a review of the curious nomenclatural history.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Minuartia obtusiloba, an amphi-Beringian species, sometimes forms hybrid swarms with M. arctica. Specimens labeled Arenaria sajanensis Willdenow ex Schlechtendal from western North America, sometimes referred to M. biflora (e.g., H. J. Scoggan 1978–1979, part 3), are likely to be M. obtusiloba.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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