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The grass genera of the world

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

Danthoniastrum (J. Holub) J. Holub

~ Metcalfia

Habit, vegetative morphology. Perennial; caespitose (with slender stems). Culms 10–50 cm high; herbaceous. Culm nodes glabrous. Leaves non-auriculate. Leaf blades linear; narrow; 0.5–0.8 mm wide; setaceous (rigid, pungent); rolled (convolute); without cross venation; disarticulating from the sheaths. Ligule present; an unfringed membrane, or a fringed membrane (?-ciliolate); truncate; 1–1.5 mm long.

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

Inflorescence. Inflorescence few spikeleted, or many spikeleted; a single raceme (with few spikelets), or paniculate (? sometimes); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 12–20(–25) mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous); the rachilla extension with incomplete florets. Hairy callus present. Callus fairly short.

Glumes two; very unequal; (the longer) long relative to the adjacent lemmas; hairless; pointed; awned (the upper, or both), or awnless; carinate to non-carinate (at the most, lightly keeled); similar (lanceolate, acuminate). Lower glume 3–5 nerved (rarely 1-nerved). Upper glume 5–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets.

Female-fertile florets 2–5 (-7). Lemmas less firm than the glumes to similar in texture to the glumes (leathery); not becoming indurated; incised; 2 lobed (bidentate); deeply cleft, or not deeply cleft; awned. Awns 1 (the lateral lobes short, awnless), or 3 (the lateral lobes attenuate into awns); median, or median and lateral; the median different in form from the laterals (when laterals present); from a sinus; geniculate; about as long as the body of the lemma to much longer than the body of the lemma; entered by several veins (3). The lateral awns when present, shorter than the median (straight). Lemmas hairy (below); non-carinate; without a germination flap; 7 nerved. Palea present (linear-lanceolate); apically notched; 2-nerved; 2-keeled (the keels scabridulous). Palea keels winged. Lodicules present; 3. Third lodicule present. Lodicules free; membranous; ciliate; heavily vascularized (judging from Baum’s illustration). Stamens 3. Anthers 3–4.5 mm long. Ovary apically hairy. Styles free to their bases (very short). Stigmas 2, or 3.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small (2.7 mm long); compressed dorsiventrally; hairy on the body (over the upper 1/3). Hilum long-linear. Embryo small. Endosperm hard.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous to lacking (fairly obscure). Papillae absent. Long-cells fairly markedly different in shape costally and intercostally (narrower costally, at least in some zones); of similar wall thickness costally and intercostally (thick walled, with dense pitting). Intercostal zones exhibiting many atypical long-cells (many of them short to square or rounded). Mid-intercostal long-cells mainly rectangular; having markedly sinuous walls (the sinuosity fine, regular). Microhairs absent (and absent adaxially - militating against a danthonioid affinity). Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies tall-and-narrow. No macrohairs or prickles seen. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; horizontally-elongated crenate/sinuous, rounded, and ‘panicoid-type’ (the silica bodies small, mostly shortly horizontally elongated, with a more or less pronounced isthmus which sometimes looks like a pair of crenations!); sometimes unambiguously dumb-bell shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes (with small, round-topped ribs separating the large, flat-topped ones). Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (of small cells, in the furrows). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries in the big ribs, the minor bundles with abaxial girders and adaxial strands); forming ‘figures’ (massive ‘anchors’). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in a continuous abaxial layer (linking the bases of the abaxial girders).

Cytology. Chromosomes ‘large’.

Classification. Watson & Dallwitz (1994): Stipoideae, or Pooideae; if pooid, Poodae; Aveneae; if stipoid, Stipeae. Soreng et al. (2015): Pooideae; Phaenospermateae. 2 species.

Distribution, phytogeography, ecology. Balkan Peninsula.

References, etc. Morphological/taxonomic: Baum 1973; Scholz 1982; Clayton 1985. Leaf anatomical: studied by us - D. compactum (Holub) Holub.

Special comments. The lack of microhairs (at least on the leaves) suggest Pooideae, but three (ciliate) lodicules, hairy ovary, 3-nerved lemma awn, etc., suggest otherwise. The available morphological descriptions are inadequate, there is no reliable information on presence or absence of genuine microhairs elsewhere on the plant (Baum enigmatically refers to ‘one-celled microhairs’ on the lodicules), and the embryo structure and cytological details are unknown. Illustrations. • D. compactum, leaf blade TS: this project

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.’.