| # 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.

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: 15th June 2025. delta-intkey.com’.

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