Poaceae Barnhart
Grass family.
Poaceae, grass family.
Plants herbs; perennial herbs; caespitose, or not caespitose; less than 15 cm high, or more than 15 cm high; 0.9–150 cm high (mean 26); not vegetatively proliferating by bulbils; without milky juice; not glandular viscid. Taproot absent. Roots white, or yellow. Ground-level or under-ground stems horizontal, or vertical and often branched, or not developed horizontally or vertically underground; rhizomatous, or stoloniferous; elongate, or compact; 0.3–5 mm wide (mean 1.6). Scales present; smooth, or striate, or grooved; 0.5–40 mm long (mean 16); glabrous, or hairy. Aerial stems erect, or decumbent, or prostrate (rarely); not conspicuously jointed; not filiform; circular or oval in cross-section; glabrous, or sparsely hairy, or densely hairy, or scabrous (rarely). Branches not glaucous; epidermis not flaky. Leaves mostly basal, or distributed along the stems; alternate; distinctly distichous, or not distinctly distichous; simple; not heterophyllous; marcescent. Prophylls 0.4–30 mm long (mean 10); with smooth veins, or with scabrous veins, or with hairy veins; with pronounced keels, or lacking pronounced keels. Stipules absent. Petioles absent. Sheaths persisting; forming a conspicuous build up at the base of the plant; greyish brown; with the margins fused to the apex, or with the margins fused only in the lower part, or with the margins not fused; glabrous, or with trichomes; pubescent, or hirsute, or scabrous; collars collars present. Ligules present; 0.1–12 mm long (mean 1.8); membranous, or a fringed membrane; glabrous, or hairy; lanceolate, or ovate-oblong, or transversely oblong; apices acuminate, or acute, or obtuse, or truncate; entire, or erose, or lacerate, or cleft. Leaf bases truncate. Blades 5–350 mm long; 0.2–9 mm wide (mean 1.7); appressed to the stem, or spreading from the vertical, or reflexed; herbaceous; rolled in bud, or folded in bud; linear; with sheath auricles, or with blade auricles, or without auricles; flat, or involute, or folded; with parallel veins; midvein conspicuously larger than the lateral veins, or midvein similar in size to other veins in the leaf; bulliform cells in distinct rows on either side of the midvein, or without bulliform cells in a distinct row on either side of the midvein; not septate nodulose; adaxial surface dull; adaxial surface glabrous, or scabrous, or hairy. Blades abaxial surface glabrous, or scabrous, or hairy. Leaves not lobed. Leaf margins entire; glabrous. Conspicuous hydathodes absent. Plants bisexual.
Flowering stems about as high as the leaves, or conspicuously taller than the leaves; glabrous. Flowering culm nodes rooting at the lower nodes, or not rooting at the lower nodes; not exposed, or becoming exposed; number visible 0, or 1, or 2, or 3. Flag leaf sheaths inflated, or not inflated. Leaf or reduced bract closely associated with the base of the inflorescence without calloused tip. Flowers in inflorescences. Inflorescences spicate, or racemose, or paniculate; inflorescence terminal; inflorescence dense, or diffuse; inflorescence linear, or oblong, or lanceolate, or ovate; inflorescence 0.4–20 cm long (mean 5.4); inflorescence 2–125 mm wide (mean 22.7); inflorescence with bulbils, or without bulbils; inflorescence main axis glabrous, or scabrous, or hairy. Number of inflorescence branches at lowest node 0, or 1, or 2, or 3, or 4, or 5, or 6–7, or 8. Inflorescence primary branches 0.2–105 mm long (mean 17.6); glabrous, or scabrous; with appressed secondary branches, or with spreading secondary branches. Bisexual spike(s) without empty bracts at the base. Involucral bracts absent. Spikelets pedicellate, or sessile; disarticulating above the glumes, or disarticulating at the base of the spikelet, or disarticulating at the nodes of the main axis; laterally compressed, or dorsoventrally compressed; oblong, or lanceolate, or ovate, or oblanceolate, or obovate; 1.5–21 mm long (mean 6.3); 0.5–9.2 mm wide (mean 2.5). Florets per spikelet 0–10 (mean 3). Flowers bisexual; actinomorphic. Floral scales not reflexed; not falling early. First glume 0.02–4.6 × the length of the second glume (mean 0.9); 0.1–1.2 × spikelet length (mean 0.54); 0.05–150 mm long (mean 5); linear, or oblong, or lanceolate, or ovate, or oblanceolate; glabrous, or with trichomes; margins glabrous, or ciliate; veins 0, or 1, or 2, or 3, or 4, or 5; apex caudate, or acuminate, or acute, or obtuse, or truncate. Second glume 0.4 × as long as the spikelet or less, or 0.4–0.9 × as long as the spikelet, or as long, or longer than the spikelet; shorter than the lowest floret, or almost as long as, or longer than, the lowest floret; 0.3–150 mm long (mean 5.6); linear, or oblong, or lanceolate, or ovate, or elliptic, or oblanceolate; glabrous, or with trichomes; veins 0, or 1, or 2, or 3, or 4, or 5, or 6. Rachilla internode 0.083–22 mm long (mean 1.6). Rachilla 0.04–0.25 mm wide (mean 0.1). Rachilla internode glabrous, or scabrous, or hairy. Rachilla pronounced between the florets, or not pronounced between the florets; terminating in a well-formed floret, or terminating in a vestigial floret, or extending beyond the uppermost floret. Callus differentiated, or not differentiated; hairs 0–3.5 mm long (mean 0.67); hairs shorter than the floret, or sub-equal to the floret (rarely). Lemma 1.3–4.141–18.5 mm long; oblong, or ovate, or lanceolate, or elliptic, or obovate, or oblanceolate; keeled, or rounded on the back; lemma not strongly incurved, or lemma strongly inrolled; surface shiny, or dull; surface glabrous, or sparsely scabrous, or hairy; surface with trichomes on veins only, or on and between the veins; veins 1, or 2, or 3, or 4, or 5, or 6, or 7. Lemma apex acuminate, or acute, or rounded, or truncate; entire, or erose, or lacerate, or bifid; not ciliate, or ciliate; awned, or awnless. Awn arising from the tip, or from below the apex but above the middle, or from the middle or below, or from just above the base; 0–60 mm long (mean 3.8). Palea well developed, or vestigial, or absent; 0.2–14 mm long (mean 3.6); with glabrous veins, or with scabrous veins, or with hairy veins. Perianth reduced to lodicules. Stamens 3; filaments all equal in length; free of the corolla. Anthers yellow; 0.2–7 mm long (mean 1.6). Nectaries absent. Carpels syncarpous; 3. Gynoecia superior. Ovaries glabrous, or hairy. Styles present. Styles partially fused; base not enlarged, continuous with the achene. Styles 1, or 2. Placentation axile, or basal. Ovules 1. Fruit without calyx persisting; a caryopsis; elongate-cylindrical; indehiscent; 0.9–10 mm long (mean 2.5); sessile; dry; glabrous. Legume valves straight. Styles may persist until dehiscence but are not modified. Seeds 1.
Chromosome information. 2n = 14–42–120.
Distribution. Canada.
Ecology and habitat. Substrates, acidic, or calcareous, or halophytic, or nitrophilous; rock, gravel, sand, silt, clay, till, moss; with low organic content, or with high organic content, or peat.
Notes. Species in world 12000, genera in world 700. Genera in study region: Alopecurus, Arctagrostis, Agrostis, Calamagrostis, Elymus, Deschampsia, Dupontia, Festuca, Hierochloe, Phippsia, Pleuropogon, Poa, Puccinellia, Trisetum.
Classification. Subclass Monocotyledonae. Dahlgren’s Superorder Commeliniflorae, Order Poales.
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).