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The grass genera of the world

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

Lithachne P. Beauv.

Habit, vegetative morphology. Perennial; caespitose. The flowering culms leafy. Culms 15–60 cm high; woody and persistent, or herbaceous (wiry); unbranched above. Plants unarmed. Leaves not basally aggregated; auriculate (in the form of tiny, membranous, erect appendages in L. pauciflora), or non-auriculate; without auricular setae. Leaf blades ovate-lanceolate; broad, or narrow; 8–30 mm wide; not cordate, not sagittate (the base asymmetric); flat, or rolled (reflexing at night); pseudopetiolate; cross veined, or without cross venation; disarticulating from the sheaths to persistent; rolled in bud. Ligule present (or with a tuft of hairs in its place); an unfringed membrane (minutely ciliolate, the pseudopetiole hairy above it at least in L. pauciflora); truncate. Contra-ligule absent.

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 in different inflorescences and segregated, in different parts of the same inflorescence branch (with a terminal male panicle (sometimes absent), and axillary infloresences reduced to a single female spikelet or the latter with males below). The spikelets overtly heteromorphic.

Inflorescence. Inflorescence determinate, or indeterminate (2-many inflorescences per node in L. pauciflora); a single raceme, or paniculate (few-flowered axillary racemes or panicles, terminated by female spikelets, or reduced to two spikelets, female above and male below. Terminal panicle if present male); spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes ‘racemes’, or paniculate; persistent. Spikelets not secund; pedicellate (male pedicels shorter than female, the latter expanded above).

Female-sterile spikelets. The male spikelets smaller than the female, reduced to lemma, palea and 2–3 free stamens. Rachilla of male spikelets terminated by a male floret. The male spikelets without glumes; without proximal incomplete florets; 1 floreted. Male florets 1; 2–3 staminate.

Female-fertile spikelets. Spikelets 6–8 mm long (triangular); compressed laterally; disarticulating above the glumes; with a distinctly elongated rachilla internode above the glumes (the segment under the floret being distinctly swollen). Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus short (columnar).

Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; pointed (ovate-acuminateto caudate); awnless; non-carinate (rounded on the back); similar (membranous). Lower glume 9–11 nerved. Upper glume 9–11 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas bony, dorsally gibbous and asymmetrical; saccate; decidedly firmer than the glumes; smooth (shiny); becoming indurated; entire; blunt (hooded); awnless; hairless; glabrous; non-carinate (dorsally rounded); with a clear germination flap; 7 nerved; with the nerves confluent towards the tip. Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma; indurated; several nerved (3); keel-less. Lodicules present (tiny, in L. pauciflora); 3; free; glabrous; heavily vascularized. Stamens 0. Ovary apically glabrous. Styles fused (into one). Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; somewhat compressed laterally. Hilum long-linear. Embryo small. Endosperm hard; without lipid.

Seedling with a short mesocotyl. First seedling leaf without a lamina (the seedling with two sheaths).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (and abundant intercostally). Intercostal papillae over-arching the stomata (but only from the subsidiaries); several per cell (small, circular, thick walled - several rows per cell, and a pair on each subsidiary). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present (very abundant); panicoid-type; 52–57 microns long (in pauciflora); 4.5–5.7 microns wide at the septum. Microhair apical cells 22.5–25.5 microns long. Microhair apical cell/total length ratio 0.39–0.47. Stomata common; (24–)27–30 microns long (in L. pauciflora). Subsidiaries papillate; triangular (sharp pointed). Guard-cells noticeably sunken, but the guard cells not noticeably overlapped. Intercostal short-cells common; not paired (mostly solitary). Costal short-cells conspicuously in long rows. Costal silica bodies intergrading oryzoid and ‘panicoid-type’; cross shaped (many fat, almost square), or dumb-bell shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; with arm cells (almost certainly, but the material seen very poor); with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Midrib conspicuous (via the large bundle with its heavy sclerenchyma girders); with one bundle only. Bulliforms present in discrete, regular adaxial groups (these wide); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (all the bundles with an anchor or an I). Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 11. 2n = 22 and 44. 2 and 4 ploid.

Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 4 species.

Distribution, phytogeography, ecology. West Indies, Central and South America.

Shade species.

References, etc. Morphological/taxonomic: Soderstrom 1980. Leaf anatomical: studied by us - L. pauciflora Beauv.

Illustrations. • L. pauciflora, as L. axillaris: P. Beauv. (1812). • L. pauciflora: Hitchcock (1936), W.I. Grasses.. • L. pauciflora: Nicora & Rúgolo de Agrasar (1987). • L. pauciflora spikelet close-up: this project. Lithachne pauciflora. Thin glumes beneath an extended internode; saccate, indurated, shiny female-fertile lemma (right), palea (left) of similar texture. • L. pauciflora, abaxial epidermis of leaf blade: this project

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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.’.