Duthiea Hackel
Including Thrixgyne Keng, Triavenopsis Candargy
Habit, vegetative morphology. Perennial; rhizomatous, or caespitose. Culms 20–70 cm high; herbaceous; unbranched above. Young shoots intravaginal. Leaves not basally aggregated (often overtopping the inflorescence); non-auriculate. Leaf blades linear; narrow; 2–6 mm wide; flat, or rolled (usually convolute); not pseudopetiolate; without cross venation; an unfringed membrane; not truncate; 5–8 mm long (lacerate).
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence few spikeleted, or many spikeleted; a single raceme, or paniculate (the lower nodes with well developed collars); contracted (the spikelets often gathered into a short unilateral cluster); spatheate (the lowest spikelet and sometimes some others subtended by a deciduous, membranous scale of unknown homology); not comprising ‘partial inflorescences’ and foliar organs. Spikelets secund (the raceme unilateral), or not secund; pedicellate.
Female-fertile spikelets. Spikelets 15–25 mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy, or hairless; the rachilla extension with incomplete florets, or naked. Hairy callus present.
Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; pointed (acute to acuminate); slightly awned to awnless; non-carinate; similar (membranous with thinner margins). Lower glume 5–9 nerved. Upper glume 7–13 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets when present, distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets (1–)2–3(–9). Lemmas ovate; similar in texture to the glumes to decidedly firmer than the glumes (herbaceous to leathery, with thin margins and tip); incised; 2 lobed; deeply cleft to not deeply cleft (from bidentate to cleft to a third or more); awned. Awns 1; median; from a sinus; geniculate; much longer than the body of the lemma; entered by one vein. Lemmas hairy. The hairs in tufts; in transverse rows (the tufts in a median horizontal row). Lemmas non-carinate; without a germination flap; 9–13 nerved. Palea present; relatively long; apically notched; awnless, without apical setae, or with apical setae to awned (sometimes 2-aristulate); 2-nerved; 2-keeled. Palea keels wingless. Lodicules absent. Stamens 3. Anthers penicillate. Ovary hairy. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit beaked via the persistent style; hairy on the body. Hilum long-linear. Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation fairly conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (the costals smaller); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls (and pitted). Microhairs present (possibly - one doubtful example seen), or absent (?). Stomata absent or very rare. Intercostal short-cells absent or very rare. Costal prickles present. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies few (though abundant adaxially); ‘panicoid-type’; more or less nodular.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib seemingly not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (at bases of furrows); in simple fans (these small). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (the large bundles with T’s and anchors). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups (of 1–3 cells); abaxial-hypodermal, the groups isolated (opposite the furrows).
Cytology. Chromosome base number, x = 7. Haploid nuclear DNA content unknown, but the chromosomes ‘large’.
Taxonomy. Pooideae, or Arundinoideae; if pooid, Poodae; Aveneae (?); if arundinoid, Danthonieae (?).
Distribution, ecology, phytogeography. 3 species; Himalayas. Species of open habitats. Mountain slopes.
Holarctic and Paleotropical. Tethyan. African. Irano-Turanian. Saharo-Sindian.
References, etc. Leaf anatomical: this project.
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).