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The grass genera of the world

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

Dichaetaria Nees

Habit, vegetative morphology. Perennial; caespitose (on a creeping, woody stock). Culms 75–100 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves mostly basal; non-auriculate. Sheath margins free. Leaf blades narrow; 4–7 mm wide; flat; without cross venation. Ligule a fringed membrane. Contra-ligule present (the adaxial fringe continuing around the back of the leaf).

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

Inflorescence. Inflorescence paniculate; open; without capillary branchlets (but the axes very slender); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; shortly pedicellate.

Female-fertile spikelets. Spikelets morphologically ‘conventional’ (until the G1 abscises); about 12 mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes (G1 caducous, G2 persisting after the spikelet has fallen). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present. Callus long; pointed.

Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas (G2 about 2/3 of the lemma length); free; hairless; pointed; awnless (but sometimes sub-aristate); non-carinate (rounded on the back); similar (narrowly lanceolate). Lower glume 3 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1; clearly specialised and modified in form (the short length of rachilla distal to L1 terminating in an empty, long, awn-like, recurved organ, which is minutely 2-aristate above the middle, very similar in form to the fertile lemma, with no sign of associated glumes). Spikelets without proximal incomplete florets.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes; not becoming indurated (but firm, leathery); incised; awned. Awns 1; median; from a sinus (the long awn arising between/behind 2 minute setae); non-geniculate; hairless; about as long as the body of the lemma (up to 10 mm long). Lemmas hairless; glabrous; non-carinate (rounded on the back); without a germination flap; 3 nerved. Palea present (long and narrow); relatively long (equalling the lemma); entire (pointed); with apical setae; thinner than the lemma (membranous); not indurated; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; not toothed; heavily vascularized. Stamens 3. Ovary apically glabrous; with a conspicuous apical appendage (the styles terminal on this - see fruit description). Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small to medium sized (about 9 mm long, with a peculiar, small, glabrous, fleshy beak, pointed above, terminating in the styles); linear; longitudinally grooved. Hilum long-linear. Pericarp thin; fused. Embryo small; slightly waisted. Endosperm hard; containing compound starch grains. Embryo without an epiblast; with a scutellar tail.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (but the intercostals larger); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls (these pitted). Microhairs present; panicoid-type (fairly broad, but very thin walled). Stomata common (in single files). Subsidiaries mostly low dome-shaped (a few approaching parallel-sided). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Costal short-cells conspicuously in long rows, or predominantly paired, or neither distinctly grouped into long rows nor predominantly paired (varying from vein to vein). Costal silica bodies saddle shaped, oryzoid, and ‘panicoid-type’ (a most unusual mixture, with intermediate forms); when identifiably panicoid type, cross shaped, butterfly shaped, and dumb-bell shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. 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 (with all the bundles); forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Arundinoideae; Arundineae (?). Soreng et al. (2015): Arundinoideae; Molinieae. 1 species (D. wightii).

Distribution, phytogeography, ecology. Southern India and Ceylon.

Mesophytic; shade species. Woodland.

References, etc. 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: 11th December 2017.’.