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The grass genera of the world

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

Alvimia Soderstrom & Londoño

Habit, vegetative morphology. Perennial. The flowering culms leafy. Culms ascending 8–25 metres into the vegetation; woody and persistent; to 1 cm in diameter; cylindrical; scandent; branched above. Buds from which the primary culm branches arise (where recorded) 1. Primary branches 10–20; clumped. The branching dendroid. Culm leaf sheaths present; deciduous; leaving a persisten girdle; conspicuously auriculate, or not conspicuously auriculate. Culm leaves with conspicuous blades. Culm leaf blades lanceolate, or ovate. Culm internodes solid, or hollow. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; auriculate; with auricular setae (inconspicuous in A. gracilis). Leaf blades linear-lanceolate to ovate-lanceolate; broad to narrow; 3–30 mm wide; rolled; pseudopetiolate; seemingly without cross venation; disarticulating from the sheaths; rolled in bud. Ligule present; a ciliate or ciliolate rim; about 0.2–0.5 mm long. Contra-ligule present.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence determinate, or indeterminate; with pseudospikelets, or without pseudospikelets; of spicate main branches and paniculate (polytelic synflorescences, terminating leafy or leafless branches); spatheate (the prophyllate pseudospikelets subtended by bracts). Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate (via the elongated terminal segment of the rachis above the empty bract).

Female-fertile spikelets. Spikelets unconventional (being indeterminate); linear; compressed laterally (?); disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets (ending in a rudimentary floret, or in a bristle-like prolongation). Hairy callus absent.

Glumes several (0–3 gemmiparous bracts, 1 or 2 empty bracts, 0 or 1 gemmiparous glume); shorter than the adjacent lemmas; awnless. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.

Female-fertile florets 3–30. Lemmas not becoming indurated; entire; awnless (or apiculate), or mucronate; non-carinate; without a germination flap. Palea present; relatively long (as long as the lemma or longer); not convolute; apically notched; awnless, without apical setae; 2-keeled. Lodicules present; 3; free; membranous; ciliate; heavily vascularized. Stamens 2 (rarely 3). Anthers 3.3–5 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous; without a conspicuous apical appendage. Styles fused (into one). Stigmas 2 (one of them sometimes branched).

Fruit, embryo and seedling. Fruit free from both lemma and palea (falling with the rachilla segment, the lemma and palea attached to its pointed base); large (10–20 mm long); reniform or olive-like; not noticeably compressed. Pericarp fleshy. Seed endospermic. Endosperm hard; containing only simple starch grains. Embryo with an epiblast; with a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins overlapping.

Seedling with a short mesocotyl. First seedling leaf without a lamina.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal (but more abundant, and much more conspicuous, intercostally). Intercostal papillae over-arching the stomata; several per cell (variable in size, irregularly lobed, some more or less coronate-pit type cf. Poa helmsii). Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (the costals generally somewhat narrower); of similar wall thickness costally and intercostally (quite thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity coarse, with heavy pitting). Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common. Subsidiaries largely covered by overarching papillae; triangular (with truncated apices). Guard-cells seemingly but not certainly overlapping to flush with the interstomatals (the stomatal complexes sunken). Intercostal short-cells very common; not paired (solitary); not silicified (or the silica poorly developed, in the material seen). With a few small costal prickles. Costal zones with short-cells. Costal short-cells conspicuously in long rows (mostly solitary, a few pairs). Costal silica bodies poorly developed, or absent; not developed, the silica cells tall-and-narrow to saddle shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Bulliforms present in discrete, regular adaxial groups; in simple fans (one in each of the slight furrows, where the fusoids from adjacent bundles approach oneanother). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); nowhere forming ‘figures’ (the girders slender). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups and in adaxial groups; abaxial-hypodermal, the groups isolated and adaxial-hypodermal, contiguous with the bulliforms (opposite the bulliforms, and laterally adjacent to them).

Classification. Watson & Dallwitz (1994): Bambusoideae; Bambusodae; Bambuseae. Soreng et al. (2015): Bambusoideae; Bambusodae; Bambuseae; Arthrostylidiinae. 3 species.

Distribution, phytogeography, ecology. Eastern coastal Bahia, Brazil.

References, etc. Morphological/taxonomic: Soderstrom and Londoño 1988. Leaf anatomical: this project.

Special comments. Fruit data wanting. Illustrations. • A. auriculata, transverse section of leaf blade: this project. • A. suriculata, transverse section of leaf blade: this project. Alvimia auriculata. Fusoids, arm cells, ‘extra’ sclerenchyma contiguous with bulliforms


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: 13th November 2017. delta-intkey.com/grass’.

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