Cerastium regelii Ostenfeld

Desjardins, Émilie, Lai, Sandra, Payette, Serge, Dubé, Martin, Sokoloff, Paul C., St-Louis, Annie, Poulin, Marie-Pier, Legros, Jade, Sirois, Luc, Vézina, François, Tam, Andrew & Berteaux, Dominique, 2021, Survey of the vascular plants of Alert (Ellesmere Island, Canada), a polar desert at the northern tip of the Americas, Check List 17 (1), pp. 181-225 : 195-196

Cerastium regelii Ostenfeld

Figure 6B, C

Materials examined. CANADA – Nunavut • Ellesmere

Island, CFS Alert; 82°29′09″N, 062°00′03″W; 36 m a.s.l.; 30 Jul. 2019; habitat: mesic in a slope, with hummocks made of till and rocks, dominated by Stellaria longipes and moss; QFA0635520 • same locality; 82°26′48″N, 062°26′12″W; 178 m a.s.l.; 28 Jul. 2019; habitat: wetland, with peat and rocks as substrates, dominated by Alopecu- rus magellanicus and moss; QFA0635576 .

Identification. Plants 1–5 cm high; herbaceous; caespitose. Taproots and rhizomes present. Stems 1–4 cm long; prostrate, decumbent, or ascending; hairy, with septate non-glandular hairs. Axillary branches present. Leaves basal and cauline; isomorphic; opposite; petiolate (basal leaves) or sessile (cauline leaves). Petiole 1.4–2.0 mm long; hairy. Basal leaf blades 3–6 mm long, 1.8–3.0 mm wide; elliptic or ovate; abaxial and adaxial surfaces both glabrous; margins glabrous or ciliate, with septate nonglandular hairs; apices obtuse. Cauline leaf blades 2.8– 4.8 long, 0.5–1.7 mm; abaxial and adaxial surfaces both glabrous; margins ciliate, with septate non-glandular hairs; apices obtuse. Inflorescence a solitary flower or a dichasium with 2 flowers. Bracts 2–4 mm long, 1–2 mm wide; surface hairy; margins hyaline (≤ 0.1 mm wide) and ciliate. Pedicels hairy. Sepals 5; 4–5 mm long, 1–3 mm wide; lanceolate or elliptic; green and purple-tinged, with hyaline margins; surface hairy, with septate nonglandular hairs and spetate-glandular hairs; margins ciliate; apices acute. Petals 5; 5.1–8.0 mm long, 2.3–5.0 mm wide; obtriangular, oblanceolate, or obovate; notched; white. Androecium with 7–10 stamens and 0.6–1.2 mm long, pale yellow anthers. Gynoecium with 5 styles and 1 stigma per style. Fruit a capsule; 8.0– 10.4 mm long, 2–3 mm wide; cylindrical; straw-colored; ending with 8–10 teeth; glabrous.

Cerastium regelii differs from C. alpinum , C. arcticum , C. beeringianum , and C. bialynickii by having shiny, glabrous leaf surfaces, whereas the four latter species have dull, densely hairy leaves ( Aiken et al. 2007).