Description: Perennial or annual herbs, usually with a taproot; stems prostrate to decumbent or rarely erect.
Leaves opposite; stipules sheathing, bearing bristles.
Inflorescence a pedunculate terminal head of numerous flowers subtended by 2–4 leafy involucral bracts. Calyx tube short, lobes 4–8, usually ciliate, eventually falling from top of mature mericarps. Corolla 3–6-lobed. Stamens 4 or 6, inserted near top of corolla tube, usually exserted. Ovary usually 3- or 4-locular, each with 1 ovule.
Fruit dehiscing into usually 3 or 4, 1-seeded mericarps.
Distribution and occurrence: World: 15 species, tropical & subtropical America. Australia: 4 species (naturalized), Qld, N.S.W.
Text by T. A. James & W. K. Allen
| ||Key to the species|| |
|1||Stems mostly more than 15 cm long; leaves up to 6.5 cm long; calyx lobes 6; mericarps 3, papillose||2|
|Stems mostly to 15 cm long; leaves up to 2.5 cm long; calyx 4 or 5 lobed; mericarps usually 4, smooth||3|
|2||Mericarps with long, acute papillae, adaxial face broad with a definite raised median ridge; leaves to 28 mm wide, hispid; stems mostly prostrate||Richardia brasiliensis|
|Mericarps with short papillae; adaxial face closed to a narrow groove; leaves to 13 mm wide, sparsely hispid; stems decumbent to erect|
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|3||Involucral bracts mostly broad-ovate, to 10 mm wide, both surfaces hispid; margins of leaves not revolute; stems densely hispid, often rooting at the nodes||Richardia humistrata|
|Involucral bracts narrow-ovate, to 5 mm wide, upper surface mostly glabrous; margins of leaves usually revolute; stems glabrous to hirsute|
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