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The grass genera of the world

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

Acostia Swallen

Named for M. Acosta-Solis, collector of the type specimen.

~ Digitaria, Panicum

Habit, vegetative morphology. Slender perennial; densely caespitose. Culms 25–40 cm high; herbaceous. Culm nodes hairy to glabrous. Sheaths keeled above. Leaf blades narrow; 3–4 mm wide (7–13 cm long, narrowed to both ends); flat; without cross venation; persistent. Ligule a fringed membrane; very short.

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

Inflorescence. Inflorescence of spicate main branches; non-digitate. Primary inflorescence branches 3–4 (these appressed, rather distant, up to 4.5 cm long). Rachides neither flattened nor hollowed, not winged. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary and paired; secund; pedicellate (the pedicels shorter than the spikelets).

Female-fertile spikelets. Spikelets 2–2.5 mm long; abaxial; compressed dorsiventrally; biconvex; falling with the glumes; with conventional internode spacings. The upper floret not stipitate. Rachilla terminated by a female-fertile floret.

Glumes present; one per spikelet (or the lower vestigial); (the upper) long relative to the adjacent lemmas; densely hairy; pointed (beyond the fruit); awnless; non-carinate. Upper glume 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. The proximal lemmas awnless; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas (as long as the spikelet); densely hairy.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes; smooth; entire; awnless; hairless; glabrous; non-carinate; having the margins inrolled against the palea; with a clear germination flap (?). Palea present; not convolute; awnless, without apical setae. Ovary apically glabrous (?). Stigmas 2 (?).

Fruit, embryo and seedling. Fruit small (1.7 mm long).

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 1 species (A. gracilis).

Distribution, phytogeography, ecology. Ecuador.

Glycophytic (riverbanks).

References, etc. Morphological/taxonomic: Swallen 1968.

Special comments. Fruit data wanting. Anatomical data wanting.


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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: 13th November 2017. delta-intkey.com/grass’.

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