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The grass genera of the world

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

Reitzia Swallen

Habit, vegetative morphology. Perennial; densely caespitose. The flowering culms leafy. Culms about 10–25 cm high (?); herbaceous; unbranched above. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; without auricular setae. Leaf blades broad; 12–20 mm wide (4–7.5 cm long, acute); not cordate, not sagittate (‘sub-truncate’ and slightly asymmetrical at base); pseudopetiolate.

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 mixed in the inflorescence (each panicle with a few female spikelets, each accompanied by 1–2 males). The spikelets overtly heteromorphic; all in heterogamous combinations.

Inflorescence. Inflorescence indeterminate (a synflorescence); of reduced axillary and terminal racemelike panicles; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes persistent. Spikelets paired, or in triplets; not secund (?); pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations (each female with 1–2 males). The ‘shorter’ spikelets male-only. The ‘longer’ spikelets female-only.

Female-sterile spikelets. Male spikelets 3 mm long, without glumes, lemma thin and 3-nerved, stamens 3. 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.

Female-fertile spikelets. Spikelets about 6 mm long; lanceolate; compressed dorsiventrally; disarticulating above the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Callus absent.

Glumes two; pointed (acuminate to attenuate); non-carinate; similar (leathery). Lower glume 3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas becoming mottled with purple; becoming indurated (presumably); awnless; hairless; non-carinate; 3 nerved (the nerves white - according to Swallen), or 5 nerved (Calderón & Soderstrom). Palea present; indurated (presumably). Stamens 0. Stigmas 2 (with long processes, plumose, not curling).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal (but largely absent from the mid-intercostal regions). Intercostal papillae over-arching the stomata; several per cell (small, circular, numerous, in rows on the costal long-cells, scattered over the intercostals bordering the costae, and concentrated in rings around the stomatal crypts). Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally to differing markedly in wall thickness costally and intercostally (the costals thicker walled in places). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity coarse, fairly irregular). Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common. Subsidiaries papillate (two per cell, overlying the guard-cells); dome-shaped and triangular. Guard-cells seemingly overlapped by the interstomatals (the stomata in depressions between the interstomatals, overhung by the small papillae). Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies crescentic, tall-and-narrow, cross-shaped, and vertically elongated-nodular (mainly a slim version of the latter). With numerous intercostal prickles. Costal short-cells conspicuously in long rows (over the main veins), or predominantly paired (over minor veins). Costal silica bodies present and well developed; ‘panicoid-type’; cross shaped to dumb-bell shaped (large); sharp-pointed.

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

Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 1 species (R. smithii).

Distribution, phytogeography, ecology. Brazil.

Shade species.

References, etc. Morphological/taxonomic: Swallen 1956. Leaf anatomical: studied by us.

Special comments. Fruit 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: 11th December 2017.’.