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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Agrostopoa Davidse, Soreng & Peterson

Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 7–29 cm high; herbaceous; branched above. Culm internodes hollow. Young shoots mainly intravaginal. Leaves mostly basal; non-auriculate. Sheath margins free. Leaf blades linear; narrow; 0.8–5 cm long, to 1.5 mm wide; folded; persistent. Ligule an unfringed membrane; entire to deeplylacerate; 0.3–3.5 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets hermaphrodite.

Inflorescence. Inflorescence 1–4 cm long, paniculate (with recurved synflorescences); open. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelets solitary; not secund; pedicellate (the pedicels fragile, breaking near the base).

Female-fertile spikelets. Spikelets 2.4–5.6 mm long; oblong; compressed laterally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; very unequal to more or less equal; about equalling the spikelets to exceeding the spikelets; shorter than the adjacent lemmas to long relative to the adjacent lemmas; hairless; glabrous, or glabrous and scabrous (apically and on the nerves); pointed; awnless; carinate; similar. Lower glume 0.66–1 times the length of the upper glume; 1 nerved. Upper glume 1 nerved, or 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas similar in texture to the glumes (thinly chartaceous); not becoming indurated; entire to incised; when incised, 2 lobed; not deeply cleft; mucronate, or awned. Awns or mucros 1; median; from a sinus (shallowly), or apical; non-geniculate; straight, or recurving, or flexuous; hairless (scabrous); much shorter than the body of the lemma to much longer than the body of the lemma (2–5.6 mm long); persistent. Awn bases twisted; not flattened. Lemmas hairless; glabrous; carinate. The keel wingless. Lemmas without a germination flap; 5 nerved. Palea present; relatively long; somewhat thinner than the lemma (Hyaline to thinly chartaceous); 2-nerved; 2-keeled. Palea keels wingless; smooth or slightly scabrous with distal hooks. Lodicules present; 2; free; membranous; glabrous; lanceolate, not toothed; not or scarcely vascularized. Stamens 2 (rarely), or 3. Anthers 1.6–2.7 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases; free. Style bases adjacent. Stigmas 2.

Fruit, embryo and seedling. Disseminule a free caryopsis. Fruit free from both lemma and palea; small (1–2 mm long); fusiform; compressed laterally. Hilum short. Pericarp thin; fused. Embryo small.

Abaxial leaf blade epidermis. Microhairs absent.

Transverse section of leaf blade, physiology. C3.

Classification. Watson & Dallwitz (1994): not described separately. Soreng et al. (2015): Pooideae; Poodae; Poeae; Poinae. 3 species (A. barclayae, A. wallisii, A. woodii).

Distribution, phytogeography, ecology. Northern Columbia.

At elevations of 3450–4500 m.

References, etc. Morphological/taxonomic: Davidse, Soreng and Peterson (2009).

Special comments. Anatomical data wanting.


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: 13th November 2017. delta-intkey.com/grass’.

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