Poa arctica R. Brown subsp. arctica

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 : 208-209

Poa arctica R. Brown subsp. arctica

Figures 11H

Materials examined. CANADA – Nunavut • Ellesmere Island, CFS Alert ; 82°26′26″N, 062°01′49″W; 147 m a.s.l.; 23 Jul. 2019; habitat: wetland on the margins of a lake, with peat as substrate, dominated by moss and Luzula nivalis ; QFA0635534 .

Identification. Plants 5.3–12.5 cm high; herbaceous; not caespitose. Fibrous roots and rhizomes present. Stems 2.5–10.0 cm long; erect or ascending; glabrous. Leaves basal and cauline. Sheath margins glabrous. Ligules 1.3– 1.7 mm long. Basal leaf blades 21–26 mm long, 0.6–0.8 (1.5–1.8 flat) mm wide; linear; rolled or folded in bud; abaxial surface glabrous and scabrous apically; adaxial surface glabrous; margins scabrous. Flag leaf blades 12.5–13.9 mm long, 0.7–0.9mm wide.Inflorescence a dif- fuse panicle; 21.0– 31.5 mm long. Branches at lowest inflorescence node 1–3; 10–22 mm long. Pedicels scabrous. Spikelets 3.7–5.1 mm long, 0.9–2.3 mm wide. Florets per spikelet 1–4. First glumes 2.6–3.2 mm long; lanceolate; surface glabrous; margins glabrous; apices acuminate. Second glumes 3.1–3.5 mm long (shorter than, or almost as long as, the lowest floret); lanceolate or ovate; veins 3; surface glabrous and scabrous on midvein; margins glabrous; apices acute. Lemmas 3.1–3.5 mm, long 1.0– 1.2 mm wide; ovate or lanceolate; keeled; veins 5; surface dull, glabrous, and hairy, with hairs on and between the veins proximally; apices acute or erose, and glabrous; awnless. Palea 2.4–3.5 mm long; veins hairy, with short (proximally) and long hairs (in the middle) (hairs also present between the veins). Rachilla between first and second lemmas 1.1–2.0 mm long. Androecium

with 3 stamens and 1.3–1.5 mm long anthers. Gynoecium with 2 styles.

Two Poa species present on Ellesmere Island have rhizomes ( P. arctica subsp. arctica and P. pratensis subsp. arctica and subsp. caespitans ; GBIF 2020). They can be differentiated based on the following: P. pratensis subsp. colpodea has at least some bulbiferous spikelets (in contrast to the others that do not have bulbils at all; Aiken et al. 2007); P. arctica subsp. arctica has open, pyramidal inflorescences, whereas both P. pratensis subspecies have usually contracted, lanceolate or narrowly pyramidal inflorescences ( Aiken et al. 2007; Saarela et al. 2020); and P. arctica subsp. arctica has paleas softly puberulent between keels, whereas both P. pratensis subspecies have paleas glabrous between keels ( Saarela et al. 2020).