| # The grass genera of the world |

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

### Hyalopoa (Tzvelev) Tzvelev

~ Colpodium

Habit, vegetative morphology. Perennial; caespitose. Culms 15–70 cm high; herbaceous; unbranched above. Culm nodes glabrous. Leaves not basally aggregated. Leaf blades narrow; 1–6 mm wide (by 4–15 cm long); flat; not pseudopetiolate; without cross venation; persistent.

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

Inflorescence. Inflorescence paniculate; open (effuse, nodding, the branches flexuose); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not in distinct ‘long-and-short’ combinations.

Female-fertile spikelets. Spikelets 5–10 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus absent. Callus short; blunt.

Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; not pointed (rounded-denticulate); awnless; non-carinate; similar (cuneate to lanceolate, often purple-tipped). Lower glume longer than half length of lowest lemma; 1 nerved. Upper glume 1 nerved, or 3 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.

Female-fertile florets 2–4. Lemmas decidedly firmer than the glumes (leathery below); not becoming indurated; entire, or incised (very slightly); pointed, or blunt; not deeply cleft; awnless; hairy (pilose below, between the ciliate nerves); carinate. The keel slightly winged. Lemmas without a germination flap; 3 nerved, or 5 nerved. Palea present; relatively long; awnless, without apical setae; 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; membranous; glabrous; not toothed; not or scarcely vascularized. Stamens 3. Anthers 1.5–3.5 mm long. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small (1.8–2.5 mm long). Hilum short. Embryo small.

Cytology. Chromosome base number, x = 7. 2n = 42. 6 ploid. Chromosomes ‘large’.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Coleanthinae. 4 species.

Distribution, phytogeography, ecology. Caucasus, Turkey, northwest Himalaya, northeast Siberia.

Helophytic (moist upland habitats); species of open habitats; glycophytic.

References, etc. Morphological/taxonomic: Bor 1970 (under Colpodium).

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: 15th June 2025. delta-intkey.com’.

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