Raddiella Swallen
Habit, vegetative morphology. Delicate perennial (R. esenbeckii and perhaps R. minima), or annual (mostly); caespitose, or decumbent (sometimes mat-forming). The flowering culms leafy. Culms 5–30(–40) cm high; herbaceous. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; auriculate, or non-auriculate; without auricular setae. Leaf blades ovate, or elliptic (to ovate-triangular, often stringly asymmetrical and apiculate); flimsy (membranous), or neither leathery nor flimsy; narrow; 2.4–8(–11) mm wide (and only 4–15(-22 mm long); slightly to much asymmetric at their bases; pseudopetiolate; cross veined; an unfringed membrane, or a fringed membrane (?-‘membranous or membranous-ciliate’); truncate; 0.2–0.5 mm long.
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 in different inflorescences, or mixed in the inflorescence (in partial (syn)inflorescences which are axillary and all-female, terminal and all-male, or mixed). The spikelets overtly heteromorphic.
Inflorescence. Inflorescence determinate, or indeterminate (some species with synflorescences); few spikeleted; a scanty, racemelike panicle, sometimes reduced to two spikelets. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-sterile spikelets. Male spikelets shorter pedicelled than females, hyaline and early deciduous. 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 1.3–2.3(–2.7) mm long; elliptic; falling with the glumes (mostly), or disarticulating above the glumes (the glumes persistent in two species); with a characteristic, thickened and indurate interglumal internode. Rachilla terminated by a female-fertile floret. Callus absent.
Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; hairless; pointed (acute); similar (membranous-herbaceous, with basal pulvini). Lower glume 3 nerved. Upper glume 3 nerved, or 5 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes (thinly leathery); smooth to papillose; becoming indurated (bony); entire; awnless; non-carinate; having the margins inrolled against the palea; with a clear germination flap. Palea present; tightly clasped by the lemma; awnless, without apical setae. Stamens 0. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit small; ellipsoid. Hilum short (punctiform, elliptic or short-linear). Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal (abundant). Intercostal papillae several per cell (most long-cells with a single median row). Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity coarse). Microhairs present; elongated; clearly two-celled; panicoid-type; 34.5–42 microns long; 5.4–6.3 microns wide at the septum. Microhair total length/width at septum 6–7.8. Microhair apical cells 16.5–18 microns long. Microhair apical cell/total length ratio 0.4–0.5. Stomata common; 19.5–21 microns long. Subsidiaries papillate (two on each, but thin walled and relatively inconspicuous); predominantly triangular. Guard-cells overlapped by the interstomatals (slightly), or overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies vertically elongated-nodular. Short, thick-walled macrohairs with simple bases common. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies consistently oryzoid; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with adaxial palisade; insufficiently well preserved to score for arm-cells, in the material seen; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat (and thin). Bulliforms present in discrete, regular adaxial groups (a large, wide group in every intercostal zone); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (every bundle having a small I or ‘anchor’). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 10.
Taxonomy. Bambusoideae; Oryzodae; Olyreae.
Distribution, ecology, phytogeography. 7 species; West Indies and tropical America. Helophytic; glycophytic. Damp depressions and wet rocks near waterfalls.
Neotropical. Caribbean, Venezuela and Surinam, Amazon, and Central Brazilian.
References, etc. Morphological/taxonomic: Maguire et al. 1965; Zuloaga and Judziewicz 1991. Leaf anatomical: this project.
Special comments. Fruit data wanting.
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).