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The grass genera of the world

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

Lamarckia Moench mut. Koeler

After the great French biologist J.B.A.P.M. de Lamarck (1744–1829), who recognised the fact of evolution fifty years before Darwin, and even postulated a plausible (though subsequently mistranslated, misunderstood amd maligned) causal mechanism.

Type species: Type: L. aurea (L.) Moench.

Including Achyrodes Boehmer, Chrysurus Pers., Pterium Desv., Tinaea Garzia

Habit, vegetative morphology. Annual; caespitose. Culms 5–200(–300) cm high; herbaceous; branched above to unbranched above; 1–5 noded. Culm nodes exposed, or hidden by leaf sheaths; glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Sheath margins joined (for up to two thirds their length). Sheaths keeled. Leaf blades apically flat; narrow; 2.6–7.5 mm wide; not setaceous; flat; without cross venation; persistent. Ligule an unfringed membrane; not truncate; (4–)5–10.2 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite, male-only, and sterile (only the terminal spikelet in each fascicle being hermaphrodite, the other 3–4 male-only or with 3–6 empty, awnless, truncate lemmas).

Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (the spikelets in peduncled fascicles); contracted. Primary inflorescence branches borne biseriately on one side of the main axis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes disarticulating; falling entire (the clusters of 3–5 spikelets falling whole). Spikelets secund; pedicellate (the pedicels villous).

Female-sterile spikelets. The lateral, sterile spikelets reduced to the glumes and lemmas, narrow-elongated, concealing the hermaphrodite spikelets save for the awns.

Female-fertile spikelets. Spikelets 2.5–4.3 mm long; cuneate; compressed laterally; falling with the glumes (in the clusters); with a distinctly elongated rachilla internode above the glumes and with distinctly elongated rachilla internodes between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent. Callus short; blunt (glabrous).

Glumes two; more or less equal; about equalling the spikelets to exceeding the spikelets; long relative to the adjacent lemmas; hairless; pointed; awned to awnless (acuminate to shortly aristate); carinate; similar (membranous, linear-lanceolate, hyaline). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1; awned (the sterile rudiment with a long awn). Spikelets without proximal incomplete florets.

Female-fertile florets 1. Lemmas papery; not becoming indurated; entire to incised; when incised, 2 lobed; not deeply cleft (bidentate); awned. Awns 1; median; dorsal; from near the top; non-geniculate; straight, or recurving; much longer than the body of the lemma (4.7–7.2 mm long); entered by one vein. Lemmas hairless; non-carinate; 4–5 nerved. Palea present; relatively long; tightly clasped by the lemma; textured like the lemma (membranous); 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; membranous; glabrous; toothed. Stamens 3. Anthers 0.5–0.8 mm long; not penicillate. Ovary apically glabrous; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit adhering to lemma and/or palea (slightly, to the palea); small (1.6–2 mm long); ovoid or ellipsoid; ventrally longitudinally grooved; glabrous. Hilum short (elliptic). Embryo small. Endosperm liquid in the mature fruit, or hard; with lipid. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent (from material seen, but see Metcalfe’s description). Long-cells markedly different in shape costally and intercostally (many of the costals quite rectangular); of similar wall thickness costally and intercostally (quite thin walled). Mid-intercostal long-cells strongly fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; 24–28.5 microns long, or 33–36 microns long (in different specimens of L. aurea). Subsidiaries low dome-shaped, or parallel-sided. Guard-cells overlapped by the interstomatals (mostly, but only very slightly), or overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies horizontally-elongated crenate/sinuous.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade adaxially flat. Midrib conspicuous (via a prominent abaxial keel); with one bundle only; with colourless mesophyll adaxially. Bulliforms not present in discrete, regular adaxial groups (restricted to midrib ‘hinges’). Many of the smallest vascular bundles unaccompanied by sclerenchyma (and many others with only 1-celled strands). Combined sclerenchyma girders present (some of the primaries only); nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in one or two rings.

Phytochemistry. Leaves without flavonoid sulphates (1 species).

Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Dactylidinae. 1 species (L. aurea).

Distribution, phytogeography, ecology. Mediterranean to Pakistan.

Commonly adventive. Mesophytic, or xerophytic; species of open habitats. Dry places.

Economic aspects. Significant weed species: L. aurea.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, and Puccinia striiformis. Smuts from Tilletiaceae. Tilletiaceae — Entyloma.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us.

Illustrations. • L. aurea, as L. hookeriana: Griffith (1851), Icon. Pl. Asiat.. • Inflorescence and spikelets (L. aurea). • General aspect (L. aurea): Gibbs Russell et al., 1990. • L. aurea, abaxial epidermis of leaf blade: this project. • L. aurea, 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: 11th December 2017.’.