Draba lactea Adams

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 : 192-193

Draba lactea Adams

Materials examined. CANADA – Nunavut • Ellesmere Island, CFS Alert ; 82°28′14″N, 062°51′41″W; 61 m a.s.l.; 10 Jul. 2019; habitat: wetland in a mountain pass, with peat and till as substrates, dominated by Eriophorum triste (Th. Fries) Hadac & Á. Löve and moss; QFA0635551 , CAN .

Identification. Plants 3.0– 5.5 cm high; herbaceous; caespitose. Taproots present. Stems 2.0– 4.5 cm long; erect; glabrous or hairy, with sparse branched hairs (2–8 rays: Y and dendritic). Leaves basal and sometimes 1 cauline; alternate or whorled; petiolate or subsessile. Petioles 2–3 mm long; slightly winged; margins glabrous or ciliate, with simple hairs. Basal leaf blades 4.1–9.0 mm long, 0.9–2.4 mm wide; oblanceolate; bases attenuate; abaxial surface sparsely hairy, with branched hairs (2–6 rays: Y, ternate, and dendritic); adaxial surface glabrous; margins ciliate with erect or deflexed, simple hairs and branched hairs (2–4 rays: Y and dendritic); apices acute or obtuse. Inflorescence a raceme, with 2–3 flowers; slightly elon- gating as the fruit matures. Pedicels 1.5–4.5 mm long; glabrous. Sepals 4; 1.3–2.6 mm long, 1.0– 1.6 mm wide; ovate or oblong; green or purple, with hyaline margins; surface glabrous or hairy, with a few sparse simple hairs apically; margins glabrous; apices obtuse. Petals 4; 3.1– 3.9 mm, long; 1.7–2.2 mm wide; obovate; unlobed or undulating; white. Androecium with 6 stamens and 0.4–0.6 mm long anthers. Gynoecium with 1 style and 1 stigma. Fruit a silique; 1.6–4.5 mm long, 1.3–2.7 mm wide; ovate; flattened; green or purple; glabrous. Styles persisting in fruit 0.2–0.7 mm long, 0.1–0.3 mm wide. Stigmas 0.3– 0.5 mm wide; larger than the styles.

In addition to Draba lactea , five other white-flowered Draba species are present on Ellesmere Island ( D. arctica J. Vahl , D. cinerea Adams , D. fladnizensis Wulfén , D. nivalis Liljeblad , and D. subcapitata Simmons ; Aiken et al. 2007; GBIF 2020). D. lactea can be differentiated by having mainly glabrous pedicels and sepals (in contrast to D. arctica , D. cinerea , D. nivalis , and D. subcapitata ),

and glabrous fruits (in contrast to D. arctica , D. cinerea , and D. subcapitata ; Aiken et al. 2007; Garneau and Sabourin 2018). Glabrous pedicels and fruits are unique to D. fladnizensis and D. lactea , but they differ in few charac- ters: D. lactea has branched hairs (2–12 rays) rather than simple and 2-forked hairs seen in D. fladnizensis (Al- Shehbaz et al. 2010b); D. lactea has bigger petals (3–5 mm long, 1.8–3.0 mm wide) than D. fladnizensis (2.0– 2.5 mm long, 0.8–1.5 mm wide; Al-Shehbaz and Mulligan 2013; Saarela et al. 2020); and margin leaf hairs of D. fladnizensis are straight and pointing strongly forward in contrast to D. lactea whose simple hairs can be deflexed and not strongly directed forward ( Svalbard Flora 2020).