Swallenochloa McClure
Named for J.R. Swallen, agrostologist.
Sometimes referred to Chusquea
Habit, vegetative morphology. Perennial. The flowering culms leafy. Culms woody and persistent; scandent; branched above. Primary branches/mid-culm node (1–)3–7 (i.e. few). Culm sheaths persistent (the blades caducous). Culm internodes hollow (‘or pith breaking down’). Unicaespitose. Rhizomes pachymorph. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; auriculate (the auricles small), or non-auriculate; without auricular setae. Leaf blades broad; pseudopetiolate; cross veined; disarticulating from the sheaths; rolled in bud. Contra-ligule present, or absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (terminating the culm in addition to leafy or leafless lateral shoots); contracted; spicate (the lateral branches appressed); spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes paniculate; persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 5–9 mm long; compressed laterally (?); disarticulating above the glumes; disarticulating between the florets (beneath the fertile lemma). Rachilla terminated by a female-fertile floret.
Glumes two; minute, or relatively large; very unequal; shorter than the adjacent lemmas; not pointed (blunt); awnless; non-carinate; similar. Lower glume much shorter than half length of lowest lemma. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 2; sterile. The proximal lemmas awnless (with a very short subule); exceeded by the female-fertile lemmas, or exceeded by the female-fertile lemmas to more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas not becoming indurated; entire; pointed; mucronate. Palea present; relatively long; apically notched; awnless, without apical setae, or with apical setae; not indurated; several nerved; 2-keeled to keel-less (being keeled only near tip). Lodicules present; 3; free; membranous; ciliate; not toothed; heavily vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary glabrous; without a conspicuous apical appendage. Styles fused (the ovary attenuate). Stigmas 2.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (and the intercostal zones with a median astomatal zone). Papillae present; costal and intercostal (but conspicuously absent from the median, astomatal intercostal regions). Intercostal papillae over-arching the stomata; several per cell (12–20 small, thick walled, lobed or branching papillae per long-cell, in two or three iregular rows). Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (those the costal zones much smaller); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; 39–45 microns long; 6.6–10.5 microns wide at the septum. Microhair total length/width at septum 3.7–6.8. Microhair apical cells 18–24 microns long. Microhair apical cell/total length ratio 0.45–0.55. Stomata common; 27–30 microns long. Subsidiaries papillate (often with two on each). Intercostal short-cells common (in the astomatal regions); in cork/silica-cell pairs; silicified. Intercostal silica bodies crescentic. Macrohairs and prickles lacking in the material seen. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies predominantly saddle shaped and oryzoid; 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 with distinct, prominent adaxial ribs; with the ribs more or less constant in size (broad, flat topped). Midrib conspicuous; having complex vascularization. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (a conspicuous group in each furrow); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (the minor bundles with slender I’s, the primary bundles with ‘anchors’). Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 40.
Taxonomy. Bambusoideae; Bambusodae; Bambuseae.
Distribution, ecology, phytogeography. 5 species; Bolivia and Brazil to Costa Rica.
Neotropical. Caribbean.
References, etc. Morphological/taxonomic: Soderstrom 1978; Soderstrom and Calderón 1978b. Leaf anatomical: this project.
Special comments. Fruit data wanting.
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).
