Saxifraga cernua Linnaeus

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 : 217

Saxifraga cernua Linnaeus

Figure 17A, B

Materials examined. CANADA – Nunavut • Ellesmere Island, CFS Alert ; 82°25′52″N, 062°07′49″W; 296 m a.s.l.; 16 Jul. 2019; habitat: wetland in a mountain pass, with peat and rocks as substrates, dominated by moss and Saxifraga cernua ; QFA0635006 .

Identification. Plants 4–11 cm high; herbaceous; not caespitose. Fibrous roots present. Stems 3.5–10.0 cm long; erect or ascending; hairy, with septate glandular hairs. Leaves basal and cauline; heterophyllous; alternate; petiolate (basal and lower cauline leaves) or sessile (upper cauline leaves). Petioles 3–25 mm long; glabrous or hairy, with septate glandular hairs. Basal leaf blades 3–8 mm long, 3–11 mm wide; suborbicular or transversely elliptic; bases cuneate, truncate, or cordate; lobed, with 3–5 palmate, obtuse or acute lobes; green or

reddish-purple; abaxial and adaxial surfaces both glabrous; margins glabrous or ciliate. Cauline leaf blades 2–10 mm long, 1–12 mm wide; ovate or lanceolate; unlobed or lobed, with 3–5 palmate lobes; abaxial surface hairy proximally, with septate glandular hairs; adaxial surface glabrous; margins glabrous or ciliate, with septate glandular hairs. Bulbils in cauline leaf axils 1–3 mm long; dark red. Inflorescence a solitary flower. Sepals 5; 2.5–4.0 mm long, 2–3 mm wide; ovate; reddish-purple; surface hairy, with septate glandular hairs; margins ciliate; apices obtuse. Petals 5; 5–10 mm long, 4–6 mm wide; obovate; unlobed or slightly notched; white or ivory. Androecium with 8–10 stamens and 0.7–1.8 mm long anthers. Gynoecium with 2 styles.

Among the nine Saxifraga Linnaeus species present on Ellesmere Island ( S. aizoides Linnaeus, S. flagel- laris Willdenow subsp. platysepala (Trautvetter) A. E. Porsild, S. hirculus Linnaeus , S. oppositifolia Linnaeus , S. cernua , S. cespitosa Linnaeus , S. hyperborea R. Brown , S. rivularis Linnaeus , and S. tricuspidata ; GBIF 2020), only the five first species have toothed or lobed basal leaves with white, pale yellow, or purplish white petals ( Aiken et al. 2007; Saarela et al. 2020). Among them, only S. cernua has bulbils ( Aiken et al. 2007; Saarela et al. 2020). S. cespitosa has hairy adaxial leaf blade surface and hairy calyx, whereas these two sructures are glabrous in S. hyperborea , S. rivularis , and S. tricuspidata ( Aiken et al. 2007) . In addition, S. cespitosa and S. tricuspidata have sessile basal leaves, whereas S. hyperborea and S. rivularis have distinctly petiolate basal leaves ( Saarela et al. 2020). Basal leaf blades are sharply 3-toothed in S. tricuspidata , whereas S. hyperborea and S. rivularis have basal leaf blades with 2–7 rounded or obtuse lobes (Brouillet and Elvander 2009b). The petals are also spotted in S. tricuspidata but not in S. cernua , S. cespitosa , S. flagellaris subsp. platysepala , S. hyperborea , S. oppositifolia , and S. rivularis ( Aiken et al. 2007; Brouillet and Elvander 2009b)