Arctophila Rupr. ex Andersson
Habit, vegetative morphology. Perennial; rhizomatous, or stoloniferous (with thick, brittle rhizomes). Culms robust, 30–80 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow (purplish); 2–7(–13) mm wide; flat; without cross venation; persistent; rolled in bud; an unfringed membrane; not truncate (usually lacerate); 3–5 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open (with long branches, the lower often deflexed); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 2.5–8 mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present. Callus short; blunt.
Glumes two; more or less equal; shorter than the spikelets; long relative to the adjacent lemmas; hairless; pointed; awnless; non-carinate; similar (membranous, ovate, apices scarious). Lower glume longer than half length of lowest lemma; 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1; merely underdeveloped (vestigial, at the rachilla tip). Spikelets without proximal incomplete florets.
Female-fertile florets 2–7. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; not becoming indurated; entire; blunt; mucronate; hairy (at the base), or hairless; non-carinate; without a germination flap; 3–5 nerved. Palea present; relatively long; apically notched; not indurated; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed, or not toothed; not or scarcely vascularized. Stamens 3. Anthers 1.2–2 mm long; not penicillate; without an apically prolonged connective. Ovary glabrous; without a conspicuous apical appendage. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea. Embryo small; without an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower, more regularly fusiform); differing markedly in wall thickness costally and intercostally (the costals with thick, pitted walls, the intercostal walls thin and unpitted). Mid-intercostal long-cells rectangular (occasionally), or fusiform (mostly); having straight or only gently undulating walls. Microhairs absent. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals (but only slightly so). Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (solitary, infrequent). Costal silica bodies absent to poorly developed (i.e. in the infrequent costal short-cells in the material of A. fulva seen).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade ‘nodular’ in section (with broad, rounded adaxial and abaxial ribs); with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (fairly ill defined), or not present in discrete, regular adaxial groups; in simple fans (the ‘groups’ irregular). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (heavy, with all the bundles); forming ‘figures’ (mostly I-shaped). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 42 and 63. 6 and 9 ploid. Chromosomes ‘large’.
Taxonomy. Pooideae; Poodae; Poeae.
Distribution, ecology, phytogeography. 1 species; Arctic and subarctic. Helophytic; species of open habitats; glycophytic. Marshy places and pool margins.
Holarctic. Boreal. Arctic and Subarctic, Euro-Siberian, Atlantic North American, and Rocky Mountains. European and Siberian. Canadian-Appalachian.
Hybrids. Intergeneric hybrids with Dupontia (×Arctodupontia Tsvelev).
References, etc. Leaf anatomical: this project.
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘Grass Genera of the World: Descriptions, Illustrations, Identification, and Information Retrieval; including Synonyms, Morphology, Anatomy, Physiology, Phytochemistry, Cytology, Classification, Pathogens, World and Local Distribution, and References.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).