| # The grass genera of the world |

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

### Thrasyopsis L. Parodi

Excluding Paspalum

Habit, vegetative morphology. Perennial; caespitose. Culms herbaceous; unbranched above. Culm nodes hairy. Leaves mostly basal; non-auriculate. Leaf blades narrow; without cross venation; persistent. Ligule an unfringed membrane; not truncate; 1 mm long.

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

Inflorescence. Inflorescence a single spike, or of spicate main branches (with short plump spikes); digitate (the material of T. repanda seen having 1–2 spikes), or non-digitate (when consisting of only one spike). Primary inflorescence branches 1–2. Inflorescence axes not ending in spikelets. Rachides flattened (foliaceous, narrow to broad and flat). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund; biseriate; subsessile.

Female-fertile spikelets. Spikelets 4–5 mm long; compressed dorsiventrally; biconvex; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes present; two; more or less equal; long relative to the adjacent lemmas; lateral to the rachis; hairless; awnless; non-carinate; similar (herbaceous). Lower glume 6–7 nerved. Upper glume 9 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; 7–9 nerved; more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas (membranous, glabrous); not becoming indurated.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes (rigid, shining); becoming indurated (thinly); entire; pointed; awnless; hairless (shiny); non-carinate; having the margins lying flat on the palea; inconspicuously 3 nerved. Palea present; relatively long (firm); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective (but the anthers divaricate). Ovary apically glabrous. Styles fused. Stigmas 2; dark.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae not over-arching the stomata; consisting of one oblique swelling per cell to consisting of one symmetrical projection per cell. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; (33–)39–42 microns long; 5.4–6.6 microns wide at the septum. Microhair total length/width at septum 6.1–7. Microhair apical cells (15–)22.5–24(–26) microns long. Microhair apical cell/total length ratio 0.45–0.61. Stomata common; 24–28.5 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Numerous cushion-based macrohairs present. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped, butterfly shaped, dumb-bell shaped, and nodular (all forms often with points); sharp-pointed (with points on representatives of the various forms).

Transverse section of leaf blade, physiology. C4; XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles (3 large, 8 small bundles); with colourless mesophyll adaxially. Bulliforms in broad ‘fans’, extending all the way from one bundle to the next. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 2 species.

Distribution, phytogeography, ecology. Brazil.

Savanna.

References, etc. Leaf anatomical: studied by us - T. repanda (Nees) Parodi.

Special comments. Fruit data wanting.

Illustrations. • Thrasyopsis repanda, as Panicum repandum: Trinius, Species Graminum 2 (1829). • Thrasyopsis repanda, abaxial leaf blade epidemis: 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: 15th June 2025. delta-intkey.com’.

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