5. Boerhavia Linnaeus, Sp. Pl. 1: 3. 1753.
黄细心属 huang xi xin shu
Herbs annual or perennial, erect, ascending, or procumbent. Stems sometimes glandular. Leaves opposite, often unequal, petiolate, margin entire or sinuate. Inflorescences usually terminal, sometimes apparently axillary, of small umbels, often irregular, rarely 1-flowered, grouped into cymose panicles. Flowers bisexual, small; bracteoles minute, often deciduous. Perianth constricted beyond the ovary, limb campanulate, apex 5-lobed, truncate, or plicate, caducous, Stamens 1-5, included or shortly exserted; filaments connate at base. Ovary oblique, stipitate. Stigma peltate or capitate. Fruit obovoid, turbinate, clavate, or terete, small, 5-ribbed or deeply 5-angled, often rough, with sessile, sticky glands. Seed: embryo curved, cotyledons thin, broad, enclosing the thin endosperm.
Between 20 and 40 species: widespread in tropical and subtropical regions; four species in China.
All species occur in disturbed, often sandy, habitats. Boerhavia coccinea, B. diffusa, and B. repens have been much confused. This is partly because of problems with typification: the type collection of B. repens, in particular, is very far from adequate, partly because the boundaries between these rather plastic weeds are not as clearly defined as one would like them to be. It is worth noting that as early as 1849, Choisy noted five different usages of B. diffusa. Published records from China need to be treated with caution. A record of the Indian species B. crispa Heyne ex J. D. Hooker from Taiwan seems to be based on a misidentification.