Rhynchoryza Baillon
Habit, vegetative morphology. Perennial. Culms herbaceous. Culm nodes glabrous. Leaves not basally aggregated; non-auriculate; without auricular setae. Leaf blades linear; narrow; 5–10 mm wide; flat; seemingly pseudopetiolate (see illustration by Nicora and Rúgolo de Agrasar 1987); without cross venation; persistent; an unfringed membrane; not truncate (acute); large.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets unconventional (owing to extreme reduction of the glumes, cf. Oryza); about 15–25 mm long; compressed laterally; disarticulating above the glumes (in so far as these can be said to be present). Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.
Glumes present to absent (vestigial, cf. Oryza); if considered present, two; minute; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; joined; awnless. Lower glume 0 nerved. Upper glume 0 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 2 (the lower larger); epaleate; sterile (much reduced, cf. Oryza). The proximal lemmas broadly ovate, cuspidate; awnless; 3 nerved; exceeded by the female-fertile lemmas (only about 1/10 the length of the spikelet); not becoming indurated.
Female-fertile florets 1. Lemmas leathery below, with the tip beneath the awn in the form of a beak extending beyond the palea, containing transversely septate aerenchyma and specialised as a flotation device; becoming indurated; entire; pointed; awned. Awns 1; apical; non-geniculate; hairless. Lemmas hairless; carinate; without a germination flap; 5 nerved. Palea present; relatively long; textured like the lemma; several nerved; one-keeled. Lodicules present; 2; membranous. Stamens 6. Ovary glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit not noticeably compressed (‘cylindrical to somewhat hexagonal in section’). Hilum long-linear. Embryo small. Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal (in the broad stomatal zones - adjoining the costae - only). Intercostal papillae over-arching the stomata (often from the interstomatals, as well as from the subsidiaries); several per cell (round, rather irregular in size and distribution on each cell). Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; ostensibly one-celled; panicoid-type. Stomata common. Subsidiaries papillate; predominantly triangular. Intercostal short-cells common (especially in the astomatal regions); in cork/silica-cell pairs; silicified. Intercostal silica bodies narrowly oryzoid-type. Costal short-cells predominantly paired (and a few short rows). Costal silica bodies predominantly oryzoid (these abundant), or tall-and-narrow (a few, representing poorly developed oryzoids); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; with arm cells (conspicuous); with fusoids. The fusoids external to the PBS (these unusual, in that they are often in pairs contiguous on their long axes, and sometimes with a third contiguous member inside, projecting further into the intercostal region). Leaf blade adaxially flat. Midrib very conspicuous (being much enlarged and aerenchymatous, with conspicuous groups of stellate chlorenchyma); having complex vascularization (with a complete, peripheral ring of bundles, the adaxial series being smaller but not ‘inverted’, and with a few small ‘disorientated’ bundles in the internal trabeculae between the air cavities); with colourless mesophyll adaxially (and large lacunae). Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (most bundles with I’s). Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Female-fertile lemma with its tip extended beyond the palea as a conical, herbaceous beak (flotation device) composed of aerenchyma with transverse septa, tapering into an awn.
Taxonomy. Bambusoideae; Oryzodae; Oryzeae.
Distribution, ecology, phytogeography. 1 species; Paraguay to Argentina. Helophytic; glycophytic.
Neotropical. Pampas.
References, etc. Leaf anatomical: this project.
Illustrations. • Abaxial epidermis of leaf blade
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
