Grass Genera of the World

L. Watson and M. J. Dallwitz


Arctagrostis Griseb.

Habit, vegetative morphology. Robust perennial; rhizomatous. Culms 10–120 cm high; herbaceous. Culm internodes hollow. Leaves non-auriculate. Leaf blades linear; narrow; 2–7 mm wide; flat; without cross venation; an unfringed membrane; truncate; 2–5 mm long.

Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous (?).

Inflorescence. Inflorescence paniculate; open, or contracted; when contracted spicate, or more or less irregular; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 2.2–7 mm long; purplish; not noticeably compressed; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus short.

Glumes present; two; more or less equal; shorter than the adjacent lemmas; hairless (usually glabrous); pointed; awnless; carinate; similar. Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; not becoming indurated; entire, or incised; when entire pointed, or blunt; awnless, or mucronate; hairless; carinate; without a germination flap; 3–5 nerved. Palea present (similar to lemma); relatively long; textured like the lemma; not indurated; 2-nerved; obscurely 2-keeled, or keel-less. Lodicules present; 2; free; membranous; glabrous; not toothed; not or scarcely vascularized. Stamens 2, or 3. Anthers 1–3 mm long; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small. Hilum short. Embryo small. Endosperm liquid in the mature fruit.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; differing markedly in wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having straight or only gently undulating walls. Microhairs absent. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal silica bodies absent (in the material seen).

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma.

Cytology. Chromosome base number, x = 7. 2n = 28, 42, 56, and 63. 4, 8, and 9 ploid. Chromosomes ‘large’.

Taxonomy. Pooideae; Poodae; Aveneae.

Distribution, ecology, phytogeography. 6 species; Arctic America, Eurasia. Helophytic, or mesophytic; species of open habitats. Arctic, marshy tundra.

Holarctic. Boreal. Arctic and Subarctic, Euro-Siberian, and Atlantic North American. European and Siberian. Canadian-Appalachian.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia brachypodii. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Urocystis. Ustilaginaceae — Ustilago.

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).

Index