| # 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. • Lithachne pauciflora, as L. axillaris: P. Beauv. (1812). • Lithachne pauciflora: Hitchcock (1936), W.I. Grasses.. • Lithachne pauciflora: Nicora & Rúgolo de Agrasar (1987). • Lithachne 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. • Lithachne pauciflora, abaxial epidermis of leaf blade: this project.

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: 15th June 2025. delta-intkey.com’.

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