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The families of flowering plants

L. Watson and M. J. Dallwitz

Rhizophoraceae R. Br.

Including Cassipoureaceae J.G. Agardh, Hirtellaceae Horan. (p.p.), Legnotidae (Legnotidaceae) Endl., Macarisiaceae J.G. Agardh corr. Bullock, Macharisieae (Macharisiaceae) J.G. Agardh, Paletuvieraceae Lam. ex Kuntze; excluding Anisophylleaceae.

Habit and leaf form. Trees, or shrubs. Helophytic (often mangroves with stilt-roots, only the lower parts of which are subterranean). Leaves opposite (but not decussate), or whorled (Weihea); of Weihea 3 per whorl; leathery; petiolate; simple. Lamina entire; pinnately veined. Leaves stipulate. Stipules interpetiolar (sheathing the terminal bud); with colleters (inside at the base); caducous. Lamina margins entire, or crenate, or dentate.

Leaf anatomy. The leaf lamina usually dorsiventral (see illustration). Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface (abaxial); anomocytic, or anisocytic, or paracytic (sometimes mixed). Hairs present; eglandular, or glandular, or eglandular and glandular; unicellular (usually mostly, sometimes tufted). Adaxial hypodermis present (commonly), or absent. Lamina with secretory cavities. The mesophyll with sclerenchymatous idioblasts (see illustration), or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Rhizophora).

Axial (stem, wood) anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar, or penta-lacunar, or multilacunar; exhibiting on either side a trace which divides, contributing the outermost lateral traces to each of the opposite leaves (in Bruguiera, Cassipourea and Rhizophora spp.), or without split-lateral traces (in other Rhizophora spp.). Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays wide, or mixed wide and narrow, or narrow (?).

The wood diffuse porous. The vessels small, or medium; solitary, or radially paired, or in radial multiples, or clustered. The vessel end-walls scalariform, or simple, or scalariform and simple. The vessels without vestured pits; without spiral thickening. The axial xylem with tracheids; with fibre tracheids, or without fibre tracheids; with libriform fibres, or without libriform fibres; at least sometimes including septate fibres, or without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal, or paratracheal. ‘Included’ phloem absent. The wood not storied. Tyloses present, or absent.

Reproductive type, pollination. Plants hermaphrodite, or polygamomonoecious (rarely); viviparous (in mangrove species), or not viviparous. Pollination mechanism conspicuously specialized (exhibiting explosive pollen release and specialised stamen-petal arangements), or unspecialized.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’, or solitary (rarely); when solitary, axillary; when aggregated, in cymes, or in racemes, or in fascicles. The ultimate inflorescence units cymose. Inflorescences axillary. Flowers regular; (3–)4–6(–20) merous. Free hypanthium present (the hypanthium sometimes prolonged beyond the ovary), or absent. Hypogynous disk present (in hypogynous flowers), or absent; when present, intrastaminal.

Perianth with distinct calyx and corolla; 6–32; 2 whorled; isomerous. Calyx (3–)4–5(–16); 1 whorled; polysepalous; regular; commonly fleshy (or leathery); persistent; valvate. Corolla (3–)4–5(–16); 1 whorled; appendiculate (usually with both a terminal arista and filiform appendages on the lobes), or not appendiculate; polypetalous (the petals often shorter than the sepals); contorted (or infolded); commonly fleshy. Petals clawed, or sessile; deeply bifid, or bilobed, or fringed (lacerate), or entire.

Androecium 8–40. Androecial members branched, or unbranched; free of the perianth (generally inserted on the outer edge of the perigynous or epigynous disk); free of one another, or coherent (then with the filaments basally connate); generally 1 whorled (but sometimes doubtfully?). The androecial bundles when stamens bundled, opposite the corolla members (with each petal individually enclosing 1–5 stamens, cf. Rhamnaceae). Androecium exclusively of fertile stamens. Stamens 8–40; diplostemonous (often paired opposite the petals), or triplostemonous to polystemonous; filantherous, or with sessile anthers. Filaments appendiculate, or not appendiculate. Anthers introrse; bilocular, or four locular to many locular (cross partitioned, in Rhizophora); tetrasporangiate. Pollen grains aperturate; 3(–4) aperturate; colporate (to colporoidate, sometimes zonorate); 2-celled (in 3 genera).

Gynoecium 2–5(–20) carpelled (multicarpellate in Crossostylis). Carpels reduced in number relative to the perianth, or isomerous with the perianth, or increased in number relative to the perianth (?). The pistil 1–6(–20) celled. Gynoecium syncarpous; eu-syncarpous; superior to inferior. Ovary 1 locular (by failure to partition), or 2–5(–20) locular. Locules without ‘false septa’. Gynoecium when G2, median. Epigynous disk of perigynous flowers, present, or absent. Gynoecium stylate. Styles 1; apical. Stigmas 1 (shallowly to clearly lobed); lobed or capitate; generally papillate. Placentation when unilocular, apical; usually axile to apical. Ovules 2 per locule (usually), or 3–25 per locule (8–25 in Pellacalyx); pendulous; epitropous; with ventral raphe; arillate, or non-arillate; hemianatropous, or anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle, or not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3 (uninucleate); not proliferating. Synergids pear-shaped. Endosperm formation nuclear. Endosperm haustoria present; chalazal (at least in Ceriops).

Fruit fleshy (usually), or non-fleshy; dehiscent (when dry), or indehiscent; a capsule (rarely), or a berry, or a drupe. Seeds copiously endospermic. Endosperm oily (and fleshy). Seeds winged, or wingless. Embryo well differentiated. Cotyledons 2(–4). Embryo chlorophyllous; straight. Micropyle zigzag.

Seedling. Germination phanerocotylar (or viviparous).

Physiology, phytochemistry. Anatomy non-C4 type (Bruguiera, Ceriops, Pellacalyx, Rhizophora). Not cyanogenic. Alkaloids present, or absent. Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins present; cyanidin, or delphinidin. Flavonols present; quercetin, or kaempferol and quercetin. Ellagic acid present (Cassipourea), or absent (Rhizophora).

Geography, cytology. Sub-tropical to tropical. Pantropical and subtropical, concentrated in the Old World. X = 8, 9.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Rhizophorales. Cronquist’s Subclass Rosidae; Rhizophorales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Malpighiales.

Species 120. Genera 15; Anopyxis, Blepharistemma, Bruguiera, Carallia, Cassipourea, Ceriops, Comiphyton, Crossostylis, Dactylopetalum, Gynotroches, Kandelia, Macarisia, Pellacalyx, Rhizophora, Sterigmapetalum, Weihea (= Cassipourea).

General remarks. Juncosa and Tomlinson (1988) presented a taxonomic synopsis.

Economic uses, etc. Some yield wood used for underwater construction and piling, and tannins are obtained from the bark.

Illustrations. • Kandelia candel (as rheedei): R. Wight (1840). • Technical details: Cassipourea (Thonner). • Technical details: Kandelia, Rhizophora (Lindley). • TS leaf of Rhizophora conjugata and LS stem cortex of R.mangle (Solereder, 1908).

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, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 19th October 2016.’.