| # The grass genera of the world |

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

### Phaenanthoecium C.E. Hubb.

From the Greek phaenestai (becoming visible) and anthos (flower), referring to the lemmas exceeding the glumes.

Type species: Type: P. kostlinii (A.Rich.) C.E.Hubbard.

Including Danthonia koestlinni, Streblochaete koestlinii

Habit, vegetative morphology. Perennial; caespitose (culms decumbent or ascending, sometimes trailing to 2 m). Culms herbaceous; branched above. Leaves not basally aggregated; non-auriculate. Leaf blades narrowly linear; narrow; flat, or rolled (convolute); not pseudopetiolate; without cross venation. Ligule present; a fringe of hairs.

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

Inflorescence. Inflorescence determinate; without pseudospikelets; few spikeleted; a single raceme; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets shortly pedicellate.

Female-fertile spikelets. Spikelets slightly compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous). Hairy callus present. Callus very short; blunt.

Glumes two; relatively large; more or less equal (or slightly unequal); shorter than the spikelets; free; not pointed (emarginate, bilobed or obtuse); awnless; carinate (G1, somewhat), or non-carinate; similar (narrowly oblong to oblong-elliptic, membranous). Lower glume 1 nerved, or 3 nerved. Upper glume 3 nerved, or 4 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.

Female-fertile florets 5–9. Lemmas similar in texture to the glumes (membranous); not becoming indurated; incised; shortly 2 lobed; not deeply cleft; awned. Awns 3; median and lateral (the lateral lobes attenuate into long setae); the median different in form from the laterals; from a sinus; geniculate. Lemmas hairy (on the margins, otherwise glabrous). The hairs in tufts (along the margins). Lemmas non-carinate (dorsally rounded); 9 nerved. Palea present; linear-oblong; entire (obtuse or truncate); awnless, without apical setae; not indurated (membranous); 2-nerved; 2-keeled. Lodicules present (minute); 2; fleshy (cuneate); ciliate (or at least ciliolate). Stamens 3. Ovary apically glabrous; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea (loosely included); concavo-convex. Hilum long-linear (about 4/5 of the grain length). Embryo small (about a quarter of the grain length).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (the intercostals larger); of similar wall thickness costally and intercostally (walls of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type (large); (52.5–)54–60(–64.5) microns long; (6–)6.3–6.6(–8) microns wide at the septum. Microhair total length/width at septum 6.7–9.8. Microhair apical cells 21–22.5–27 microns long. Microhair apical cell/total length ratio 0.38–0.42. Stomata common; 25.5–28.5 microns long. Subsidiaries mostly high dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; almost exclusively cross shaped, butterfly shaped, and dumb-bell shaped (short); not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (all the bundles with I’s). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; incertis sedis. 1 species (P. koestlinii).

Distribution, phytogeography, ecology. Northeast Africa.

Shade species. Shady cliffs.

References, etc. Morphological/taxonomic: Hubbard 1936c. Leaf anatomical: studied by us.

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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