| # The grass genera of the world |

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

### Centrochloa Swallen

~ Axonopus

Habit, vegetative morphology. Annual; caespitose. Culms about 20–75 cm high; herbaceous; unbranched above. Culm nodes glabrous. Leaves mostly basal; non-auriculate. Leaf blades narrow; without cross venation; persistent. Ligule a fringed membrane.

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

Inflorescence. Inflorescence of spicate main branches (the rachides filiform); digitate to subdigitate. Rachides hollowed. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes with very slender rachides; persistent. Spikelets solitary; secund.

Female-fertile spikelets. Spikelets 3 mm long; turbinate; adaxial; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (as a downward-pointing hairy projection, perhaps representing the lower glume, at the base of the spikelet - cf. Digitariopsis).

Glumes one per spikelet (the upper); long relative to the adjacent lemmas; dorsiventral to the rachis; hairy (densely straight-hairy, with dark brown hairs in 4 rows between and outside the veins, and with the rows terminating apically in tufts); pointed; awnless; non-carinate. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; sterile. The proximal lemmas awnless; 2–3 nerved; more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes (cartilaginous); not becoming indurated; entire; pointed; awnless; hairless; non-carinate; having the margins lying flat on the palea; with a clear germination flap; 5 nerved. Palea present; relatively long; 2-nerved; keel-less. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Ovary apically glabrous. Stigmas 2.

Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the intercostals short and broad, the costals long and narrow); of similar wall thickness costally and intercostally (fairly thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type. Stomata common. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’.

Transverse section of leaf blade, physiology. C4; XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms not present in discrete, regular adaxial groups (constituting most of the epidermis). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Special diagnostic feature. Upper glume extended downwards into a conspicuous spur.

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

Distribution, phytogeography, ecology. Brazil.

Species of open habitats. Savanna.

References, etc. Leaf anatomical: studied by us.

Illustrations. • Centrochloa singularis, with Spheneria kegelii: Swallen, J. Wash. Acad. Sci. 25 (1935).

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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