14.11 LAMARCKIA Moench
Lynn G. Clark

Plants annual; tufted. Culms 5–40 cm, erect or decumbent at the base, glabrous. Sheaths open for at least 1/3 their length, glabrous, margins membranous and continuous with the ligules; auricles absent; ligules membranous, acute, glabrous, apices somewhat erose; blades flat, glabrous. Inflorescences panicles, dense, secund, golden-yellow to purplish; primary branches appressed to the rachis; secondary branches capillary, smooth, glabrous, flexuous, terminating in 1–4 fascicles of pedicellate spikelets, strongly bent below the junction with the fascicle base; pedicels of spikelets in each fascicle fused at the base, strigose. Spikelets dimorphic, the terminal spikelet of each fascicle fertile, the others sterile; disarticulation at the base of the fused pedicels. Fertile spikelets terete to somewhat laterally compressed, with 2 florets, 1 bisexual, the other a rudiment, borne on long rachilla internodes; calluses short, blunt, glabrous; glumes narrow, acuminate or short-awned, 1-veined; bisexual lemmas scarcely veined, each with a delicate, straight, subapical awn; paleas equal or subequal to the lemmas; lodicules 2, glabrous, toothed, anthers 3; ovaries glabrous; rudimentary florets highly reduced lemmas, each with a delicate, straight awn. Sterile spikelets linear, laterally compressed; florets 5–10; glumes similar to those of the fertile spikelets; lemmas imbricate, obtuse, unawned; paleas absent. Caryopses ovoid or ellipsoid, adhering to the lemmas and/or paleas. x = 7. Named for Jean Baptiste Antoine Pierre Monnet de Lamarck (1744–1829), a French biologist best known for his ideas about evolution by the inheritance of acquired characteristics.

Lamarckia is a monotypic genus that has been introduced into North America from the Mediterranean and the Middle East.

 

1. Lamarckia aurea (L.) Moench
Goldentop

Culms (5)10–40 cm. Ligules 3–10 mm; blades 2.5–11(20) cm long, 2.5–7.5 mm wide. Panicles 2–8 cm long, 0.9–3.2 cm wide; branches 1–2 cm, with a few scattered, whitish hairs. Fertile spikelets 2.6–4.2 mm; lower rachilla internodes about 1 mm, glabrous; upper rachilla internodes 1.4–2.2(2.6) mm, puberulent or glabrous, sometimes scabrous; glumes 2.6–4.2 mm, bisexual florets 2.4–3 mm, minutely bifid, teeth shorter than 0.2 mm, apices awned, awns 5–7.2 mm; anthers 0.4–0.7 mm; rudimentary florets 0.4–0.6 mm, awns 4–5(7) mm. Sterile spikelets 6–9 mm; lemmas 1–2 mm. Caryopses 1–2 mm. 2n = 14.

Lamarckia aurea grows on open ground, rocky hillsides, and in sandy soil, at elevations from sea level to 700 m. Within the Flora region, it is known only from the southwest. It is an attractive, but rather weedy species.