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The grass genera of the world

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

Sucrea Soderstrom

Named for Dimitri Sucre.

Habit, vegetative morphology. Perennial; rhizomatous and caespitose. Culms 30–100 cm high; herbaceous; unbranched above. Culm nodes hairy, or glabrous. Plants unarmed. Leaves mostly basal, or not basally aggregated; without auricular setae. Leaf blades broadly ovate; broad; 25–100 mm wide; pseudopetiolate; cross veined; rolled in bud. Ligule present, or absent.

Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets segregated, in different parts of the same inflorescence branch (the female spikelets terminal, the males below). The spikelets overtly heteromorphic.

Inflorescence. Inflorescence paniculate; open (terminal); spatheate (the terminal sheath constituting a spathe); not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes paniculate; persistent. Spikelets not secund; pedicellate (the pedicels of female spikelets thickened apically); not in distinct ‘long-and-short’ combinations.

Female-sterile spikelets. Male spikelets without glumes; lemma membranous, 3-nerved; palea membranous, 2-nerved; lodicules 3, fleshy; stamens 3, free, non-penicillate. Rachilla of male spikelets terminated by a male floret. The male spikelets without glumes; without proximal incomplete florets; 1 floreted. Male florets 1; 3 staminate. The staminal filaments free.

Female-fertile spikelets. Spikelets 6.5–10 mm long; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.

Glumes two; more or less equal; long relative to the adjacent lemmas (exceeding them); hairy (finely pubescent); pointed (ovate-acuminate to shortly subulate); shortly awned (with a terminal scabrid subule); non-carinate; similar (with cartilaginous margins, twisting with age, tessellate). Lower glume 5 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas fusiform, completely embracing the palea; decidedly firmer than the glumes; pitted; becoming indurated (leathery when young); awnless; hairless; glabrous; non-carinate; having the margins inrolled against the palea; without a germination flap (apparently); 5 nerved (tessellate). Palea present; relatively long (slightly shorter than the lemma); entire; awnless, without apical setae; textured like the lemma; indurated; 2-nerved (? ‘2 strong nerves and transverse veinlets’). Lodicules present; 3; free; fleshy; glabrous; heavily vascularized. Stamens 0 (3 staminodes). Ovary apically glabrous. Styles fused (the ovary attenuate into one long style). Stigmas 2.

Fruit, embryo and seedling. Hilum long-linear. Embryo small; waisted.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae not over-arching the stomata; several per cell (round, thick walled, in 2–3 irregular rows on long-cells and interstomatals, the costals with mostly only one row). Long-cells markedly different in shape costally and intercostally (the intercostals much broader); of similar wall thickness costally and intercostally (quite thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (coarsely so). Microhairs present; panicoid-type; (45–)48–51(–54) microns long; 5.4–6.3 microns wide at the septum. Microhair total length/width at septum 7.1–10. Microhair apical cells 19.5–25.5 microns long. Microhair apical cell/total length ratio 0.43–0.5. Stomata common; 21–24 microns long. Subsidiaries mostly high dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (mostly). Costal short-cells conspicuously in long rows. Costal silica bodies saddle shaped, oryzoid, and ‘panicoid-type’ (forming an almost continuous series); the panicoid form cross shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat (except for the midrib). Midrib conspicuous; having a conventional arc of bundles (a large median, and a small one on either side); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (these wide); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with most of the main bundles); forming ‘figures’ (most of the main bundles with I’s or ‘anchors’).

Cytology. Chromosome base number, x = 11. 2n = 22. 2 ploid.

Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 3 species.

Distribution, phytogeography, ecology. Brazil.

Shade species. In forest.

References, etc. Morphological/taxonomic: Soderstrom 1981c. Leaf anatomical: studied by us - S. maculata Soderstrom.

Illustrations. • S. maculata, detail of TS leaf blade: 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.’.