The grass genera of the world
Including Vilfa Beauv.
Habit, vegetative morphology. Dwarf perennial; caespitose, or decumbent. Culms 2–25 cm high; herbaceous. Leaves non-auriculate. Sheath margins joined. The upper sheaths somewhat expanded. Leaf blades linear; narrow; 1–3 mm wide; flat; without cross venation; rolled in bud. Ligule an unfringed membrane; not truncate; 1–1.5 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous (?); with hidden cleistogenes, or without hidden cleistogenes. The hidden cleistogenes when present, in the leaf sheaths.
Inflorescence. Inflorescence paniculate; open, or contracted (to spike-like); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 1–2.5 mm long; compressed laterally to not noticeably compressed (terete); disarticulating above the glumes (but the glumes also often caducous). Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus short.
Glumes present; one per spikelet, or two; minute; very unequal; shorter than the adjacent lemmas (the longer less than a third as long); free; awnless; similar (more or less caducous). Lower glume much shorter than half length of lowest lemma; 0 nerved. Upper glume 0 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes (membranous); not becoming indurated; entire; pointed, or blunt; awnless; hairy, or hairless; carinate to non-carinate; without a germination flap; 3–5 nerved. Palea present; relatively long; 2-nerved; 2-keeled. Palea keels hairy (often spinulose), or scabrous (?). Lodicules present; 2; free; membranous; glabrous; not toothed; not or scarcely vascularized. Stamens 1, or 2(–3). Anthers 0.3–0.6 mm long. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; ellipsoid (protruding from the floret when mature). Hilum short (oval). Embryo small. Endosperm hard. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation lacking (and without short-cells). Papillae absent. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common (fairly); (36–)39–42(–45) microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals (the subsidiaries also sunken). Intercostal short-cells absent or very rare. Costal zones without short-cells. Costal silica bodies absent.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade adaxially flat. Midrib conspicuous (prominent adaxially, and flanked by conspicuous bulliform hinges); with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms not present in discrete, regular adaxial groups (apart from the midrib hinges). Many of the smallest vascular bundles unaccompanied by sclerenchyma (and no sclerenchyma with any of the other bundles either, in the material of P. algida seen).
Cytology. Chromosome base number, x = 7. 2n = 28. 4 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Coleanthinae. 3 species.
Distribution, phytogeography, ecology. Arctic circumpolar, South American mountains.
Helophytic; species of open habitats.
Hybrids. Intergeneric hybrids with Puccinellia (×Pucciphippsia Tsvelev).
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia brachypodii.
References, etc. Leaf anatomical: studied by us - P. algida (Solander) R. Br.
Illustrations. • P. wilczekii: Nicora & Rúgolo de Agrasar (1987)
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The 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. Version: 11th December 2017. delta-intkey.com/grass’.