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The grass genera of the world

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

Apluda L.

From the Latin apluda (chaff), referring to conspicuously spatheate groups of spikelets, or to spathes persisting on old inflorescences.

Including Calamina P. Beauv.

Habit, vegetative morphology. Perennial; decumbent (often scrambling). Culms 50–120 cm high; branched above. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades broad (to 15 mm), or narrow; pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite, male-only, and sterile (in combination). Apomictic.

Inflorescence. Inflorescence paniculate; open; spatheate (each naviculate spathe enclosing a raceme reduced to a single joint, with 3 spikelets); a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes very much reduced (to 1 sessile and 2 pedicelled spikelets); clustered (at the tips of the usually fascicled branchlets); with substantial rachides; disarticulating (the whole triplet deciduous from the minute peduncle). Spikelets in triplets; not secund; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations (the pedicels flat and broad). Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets male-only and sterile (one male, the other reduced to a small glume).

Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; more or less equal; long relative to the adjacent lemmas; awnless; very dissimilar (lower leathery, upper thinner and naviculate). Lower glume 11 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate; male. The proximal lemmas awnless; similar in texture to the female-fertile lemmas (thinly membranous to hyaline).

Female-fertile florets 1. Lemmas less firm than the glumes; not becoming indurated; entire, or incised; when incised 2 lobed; mucronate, or awned (entire and mucronate, or deeply bilobed/awned). Awns when present, 1; from a sinus; geniculate; much shorter than the body of the lemma to much longer than the body of the lemma. Lemmas hairless; non-carinate; 1 nerved. Palea present; very reduced; not indurated (hyaline); nerveless. Lodicules present; 2; free; fleshy; glabrous. Stamens 2–3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit compressed dorsiventrally. Hilum short. Embryo large. Endosperm containing compound starch grains. Embryo without an epiblast; with a scutellar tail.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; consisting of one oblique swelling per cell (the interstomatal cells papilliform). Long-cells similar in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally (fairly thin walled). Intercostal zones with typical long-cells (but these rather short). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; 39–42 microns long; 6–7.5 microns wide at the septum. Microhair total length/width at septum 6.5–9. Microhair apical cells (12–)13.5–18 microns long. Microhair apical cell/total length ratio 0.31–0.43. Stomata common; 21–22.5(–24) microns long. Subsidiaries dome-shaped. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies ‘panicoid-type’; butterfly shaped, or dumb-bell shaped, or nodular.

Transverse section of leaf blade, physiology. C4; XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans (or in irregular groups). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 10. 2n = 20 and 40. 2 and 4 ploid. Chromosomes ‘small’.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae. 1 species (A. mutica).

Distribution, phytogeography, ecology. Mauritius & Socotra to Formosa & New Caledonia.

Mesophytic. In thickets and forest margins.

Rusts and smuts. Rusts — Dasturella and Puccinia. Taxonomically wide-ranging species: ‘Uromycesschoenanthi. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Tilletia. Ustilaginaceae — Sorosporium and Sphacelotheca.

References, etc. Leaf anatomical: Metcalfe 1960, and studied by us.

Illustrations. • A. mutica: Fl. Iraq, 1968. • A. mutica, abaxial epidermis of leaf blade: this project. • A. mutica, T.S. leaf blade midrib region: 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.’.