The Grass Genera of the World
The Grass Genera of the World | |
Habit, vegetative morphology. Diminutive perennial; caespitose. Culms 5–10 cm high; herbaceous; unbranched above. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Sheath margins free. Leaf blades linear; narrow; 1–3.5 mm wide; flat, or rolled (conduplicate); without cross venation; persistent. Ligule an unfringed membrane; truncate; 0.5 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets (but with female and sterile florets distally in the spikelet).
Inflorescence. Inflorescence few spikeleted; paniculate; contracted. Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; shortly pedicellate.
Female-fertile spikelets. Spikelets 4.5–6.5 mm long; not noticeably compressed (terete); disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes present; two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; not pointed (broadly rounded); awnless; non-carinate; similar (broad, membranous, irregularly dentate). Lower glume 3 nerved. Upper glume 5 nerved. Spikelets with incomplete florets (the lower florets hemaphrodite, female florets above, the uppermost sterile). The incomplete florets distal to the female-fertile florets. The distal incomplete florets clearly specialised and modified in form (the rachilla terminating in a clavate clump of rudiments).
Female-fertile florets 2–4. Lemmas flabelliform, irregularly toothed, often pinkish; similar in texture to the glumes; not becoming indurated; incised (emarginate or split); awnless; hairless; glabrous; non-carinate; without a germination flap; 5 nerved, or 7 nerved. Palea present; relatively long; three lobed, the median lobe itself bilobed; awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed; not or scarcely vascularized. Stamens 3. Ovary glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (1.5 mm long). Hilum short. Embryo small. Endosperm hard; with lipid; containing compound starch grains. Embryo with 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 similar in shape costally and intercostally, or markedly different in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies predominantly horizontally-elongated smooth (being at the most only slightly sinuate).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups; nowhere involved in bulliform-plus-colourless mesophyll arches. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); the girders small. Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Spikelets with the distal incomplete florets and/or the rachilla apex forming a terminal clavate appendage.
Cytology. 2n = 42.
Taxonomy. Pooideae; Poodae; Poeae.
Distribution, ecology, phytogeography. 2 species; Andes. Species of open habitats. In high mountains.
Holarctic and Neotropical. Madrean. Andean.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Miscellaneous. • Abaxial epidermis of leaf blade (A. lepidula)
This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. This is much more easily achieved using 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 specified attributes, summaries of attributes within groups of taxa, geographical distribution, classification, and species sampled for anatomy.
Cite this publication as: ‘Watson, L., 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: 6th June 2008. http://delta-intkey.com’.
