Arctagrostis latifolia (R. Br.) Griseb. subsp. latifolia
Polar grass.
Poaceae, grass family.
Ledeb., Fl. Ross. 4: 434. 1852.
Colpodium latifolium R. Br., Chlor. Melvill. 28. 1823.
Type: Canada. Melville Island, W.E. Parry, 1819–1820. (Holotype: BM! two fragments at LE, Tzvelev 1976).
Arctagrostis latifolia var. longiglumis Polunin, Bull. Natl. Mus. Canada 92 (Biol. Ser. 24): 48. 1940. Type: Canada. Nunavut: Baffin Island, Foxe Island, Nettilling Lake, 24 Aug. 1925. J.D. Soper 125636. (Holotype: CAN! Cotype: BM!).
Arctagrosits latifolia subsp. nahanniensis A.E. Porsild, Bull. Natl. Mus. Canada 171 (Biol. Ser. 64): 120. 1961. Type: Canada. N.W.T.: Mackenzie Mountains, Hole-in-wall Lake, lake shore, in sand, elev. 3800 ft., July 18, 1960. E.W. Arnold 121 (Holotype CAN!).
Colpodium latifolium R. Br.
Plants not caespitose; stems arising close together or singly (usually producing only a single culm per year in the High Arctic); less than 15 cm high, or more than 15 cm high; 10–95 cm high. Ground-level or under-ground stems horizontal; rhizomatous; elongate, or compact; 2–3 mm wide. Scales present; smooth; 8–30 mm long; glabrous. Aerial stems erect; circular or oval in cross-section; glabrous (uppermost culm node condensed in lowest 3rd of plant). Leaves distributed along the stems; alternate; marcescent. Petioles absent. Sheaths with the margins fused only in the lower part; with trichomes; scabrous (seen at magnification 40× on flag leaf sheath; uppermost culm sheath longer than the blade); collars collars present. Ligules present; 2.5–5 mm long; membranous; glabrous; transversely oblong; apices obtuse (broadly); erose, or lacerate. Blades 6–80 mm long; 2–4 mm wide (when flat); appressed to the stem, or spreading from the vertical; rolled in bud; linear; flat; with parallel veins; midvein similar in size to other veins in the leaf (mid leaf); adaxial surface scabrous. Blades abaxial surface scabrous.
Flowering culm nodes becoming exposed (lower sheaths); number visible 0–3. Inflorescences paniculate; inflorescence dense (in plants growing in cold habitats), or diffuse (branches spreading and inflorescence becoming stiffly pyramidal, when plants grow at warmer sites); inflorescence linear, or oblong, or lanceolate; inflorescence 2.5–10(–17) cm long; inflorescence 8–26 mm wide; inflorescence main axis glabrous. Number of inflorescence branches at lowest node 5 (or more). Inflorescence primary branches 5–40(–65) mm long; scabrous; with appressed secondary branches (usually), or with spreading secondary branches (in warmer habitats). Spikelets pedicellate (3–15(-40) spikelets per branch); disarticulating above the glumes; laterally compressed; oblong; (3–)4–6 mm long; 1.3–2.4 mm wide. Florets per spikelet 1 (rarely 2). Glumes sub-equal. First glume 0.8–0.9 × the length of the second glume; 0.65–0.85 × spikelet length; 1.8–4.3 mm long; lanceolate; glabrous; margins glabrous; veins 1(–3); apex acute. Second glume 0.4–0.9 × as long as the spikelet; shorter than the lowest floret (usually 1 mm or more shorter than the lemma); 2.3–5 mm long; lanceolate; glabrous; veins (1–)3. Rachilla extending beyond the uppermost floret (usually, rarely terminating in a well-formed or a vestigial floret). Callus differentiated; hairs shorter than the floret. Lemma 3–6 mm long; lanceolate; keeled (thinner in texture towards the apex); surface dull; surface sparsely scabrous (similar to lemma surface); surface with trichomes on and between the veins; veins 3–5 (lateral veins obscure, not reaching to the apex). Lemma apex acute; entire; not ciliate; awnless. Palea well developed; 3.7–5.5 mm long; with scabrous veins ( similar to the lemma in length, with a single keel at one prominent vein and the second vein faint). Perianth reduced to lodicules. Stamens 3. Anthers 1.8–4 mm long. Carpels syncarpous; 3. Gynoecia superior. Styles 2. Ovules 1. Fruit a caryopsis; indehiscent; 1.7–3 mm long; sessile; dry. Seeds 1.
Chromosome information. 2n = 28, 42, 56, and 62 (Five voucher specimens of A. latifolia with 2n = 28 were annotated by S. Aiken at LE in Feb. 1999).
Distribution. Circumpolar, or circumboreal. Arctic. Range in the Canadian Arctic Archipelago widespread. Arctic Islands: Baffin, Devon, Ellesmere, Axel Heiberg, Parry Islands, Conrwallis, Banks, Victoria, Prince of Wales, Somerset, King William, Southampton, Coats.
Ecology and habitat. Substrates, wet meadows, hummocks, around the margins of ponds, marshes, along streams (and in old stream beds), river terraces (channels, floodplains or braided flats), tundra, slopes, ridges; imperfectly drained moist areas, on seepage slopes, on solifluction slopes, dry, moderately well drained; calcareous; rock, gravel, sand, silt, clay (sometimes slumping on slopes), till, moss; with low organic content, or peat (rarely in peat bogs). Occurring in a wide range of habitats and exhibiting considerable phenotypic plasticity that appears to reflect the warmth and nutrients available in an environment. This is a circumpolar species that in the Canadian Arctic Islands is most commonly found in the warmer sectors where it is a regular, but generally not abundant, constituent of moderately to imperfectly drained tundra communities, but it is rarely a primary coloniser.
Taxon as an environmental indicator. Culm height in this species appears to be strongly correlated with environmental factors, particularly temperature. Plants growing on the sheltered or sunny side of a rocky outcrop may be conspicuously taller and have more open inflorescences than plants growing in a colder, north facing adjacent microhabitat. How open the inflorescence branching becomes also appears to be related to environmental factors. Plants with larger more spreading inflorescences occur in known thermal oases, for example, an oasis that has been documented by J. Jacobs, Dept. of Geography, Memorial University, at Burwash Bay, Nettilling Lake, Baffin Island.
Notes. The nematode Anguina agrostis Steinbuck infects spikelets and causes the ovaries to enlarge and become dark purple (Mulvey 1963). Other parts of the infected spikelet become atypical. Specimens with this infection are conspicuous and have been annotated as forma prolifera or forma vivipara, but these names have no taxonomic validity.
Porsild (1964) did not mention var. longiglumis Polunin, that was described from a thermal oasis on Baffin Island by Polunin (1940), who also described the species as "an atrocious typus polymorphous". Aiken and Lefkovitch (1990) studied the genus, documented considerable phenotypic plasticity within the species, and found only subsp. latifolia on the Arctic Archipelago, although subsp. arundinacea (Trin.) Tzvelev occurs nearby on the North American continent. No reason for recognising var. longiglumis was found.
Illustrations. • Plant habitat. Plants growing on small island in flood plane of stream on wet, calcareous silt. Nunavut, Ellesmere Island, Scoresby Bay 79°53'N, 71°33'W. S.G. Aiken 98–013. Photograph by Mollie MacCormac. • Close-up of preanthesis inflorescences. Spikelets appressed, inflorescence very narrow prior to anthesis. Nunavut, Ellesmere Island, Scoresby Bay 79°53'N, 71°33'W. S.G. Aiken 98–013. Photograph by Mollie MacCormac. • Laboratory photograph. Plants collected in Nunavut, Baffin Island, Iqaluit, S.G. Aiken 94–022. (CAN). and photograph by K. Clarkin in Ottawa. • Close-up of inflorescence. Inflorescence at anthesis photograph by K. Clarkin. S..G. Aiken 94–022. (CAN). • Close-up of inflorescence. Inflorescence at anthesis, with purple anthers, approximately 3 mm long, and white, feathery stigmas. Note that the spikelets have a single floret, the second glume is at least 1 mm shorter than the lemma, and that the palea is almost as long as the lemma and folded so that it look similar to the lemma. Photograph by K. Clarkin. Canada. Nunavut, Baffin Island, Iqaluit, S.G. Aiken 94–022. (CAN). • Holotype, ssp. nahanniensis. Holotype of taxon described as subspecies nahanniensis. Canada. N.W.T.: Nahanni Park, Hole-in-wall Lake, 1960, E.W. Arnold 121. (CAN). The locality is more than 20° latitude further south than loacility of the type for the genus, and this specimens is considered to be merely a more robust specimen of Arctagrostis latifolia that was growing in warmer conditions. (Aiken and Lefkovitch 1990). • Holotype. Holotype specimen of Arctagrostis latifolia. Canada. Nunavut, Melville Island, 1819–1820, W.E. Parry. (Holotype: BM). Photograph by L. Consaul. • Distribution map. Arctagrostis latifolia map from Aiken and Lefkovitch, Can. J. Bot. 68: 2427. Dark circles = ssp. latifolia (open squares = subsp. arundinacea, see excluded taxa).
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L.Consaul, R.L. Boles, R. Elven and M.E. LeBlanc. 2001 onwards. Flora of the Canadian Arctic Archipelago. Volume 1. Pteridophytes and Monocotyledons: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 16th March 2001. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Aiken, Dallwitz et al. (1999) should also be cited (see References).
