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.
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 narrow; 2.6–7.5 mm wide; not setaceous; flat; without cross venation; persistent; an unfringed membrane; not truncate; (4–)5–10.2 mm long.
Reproductive organization. Plants bisexual, 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 glabrous. 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.
Taxonomy. Pooideae; Poodae; Poeae.
Distribution, ecology, phytogeography. 1 species; Mediterranean to Pakistan. Commonly adventive. Mesophytic, or xerophytic; species of open habitats. Dry places.
Holarctic and Paleotropical. Boreal and Tethyan. African. Euro-Siberian. Mediterranean. Saharo-Sindian. European.
Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, and Puccinia striiformis. Smuts from Tilletiaceae. Tilletiaceae — Entyloma.
Economic importance. Significant weed species: L. aurea.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • Inflorescence, spikelets. • General aspect. • Abaxial epidermis of leaf blade. Lamarckia aurea. • Abaxial epidermis of leaf blade. Lamarckia aurea.
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).
