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The families of flowering plants

L. Watson and M.J. Dallwitz

Sonneratiaceae Engl. & Gilg

Alternatively Blattiaceae; ~ Lythraceae.

Including Duabangaceae Takhtajan

Habit and leaf form. Shrubs (Sonneratia comprising mangroves, with vertical branches of the root system projecting into the air above the mud), or lianas. Self supporting, or climbing. Helophytic, or mesophytic. Leaves opposite, or whorled; leathery; petiolate, or subsessile; not gland-dotted; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial (isobilateral in Sonneratia). Stomata in Sonneratia on both surfaces; paracytic. The mesophyll containing mucilage cells; with sclerenchymatous idioblasts.

Axial (stem, wood) anatomy. Cork cambium in Sonneratia, present; initially superficial. Primary vascular tissues in a cylinder, without separate bundles; bicollateral. Internal phloem present. Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow.

The wood diffuse porous. The vessels mostly medium and large; moderately solitary to radially paired. The vessel end-walls simple. The vessels with vestured pits. The axial xylem without fibre tracheids; with libriform fibres; including septate fibres (in Sonneratia), or without septate fibres. The fibres without spiral thickening. The parenchyma paratracheal (in Duabanga, absent in Sonneratia). The secondary phloem not stratified. ‘Included’ phloem absent. The wood not storied. Tyloses often present.

Reproductive type, pollination. Plants hermaphrodite (usually), or monoecious, or polygamomonoecious (?); homostylous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes, or in corymbs. The ultimate inflorescence units cymose. Inflorescences terminal; 1–3 flowered cymes or corymbs. Flowers medium-sized to large; regular; cyclic; polycyclic. Free hypanthium present (thick). Hypogynous disk present.

Perianth with distinct calyx and corolla, or sepaline (corolla sometimes lacking); 8–16; 1 whorled, or 2 whorled; isomerous. Calyx 4–8; 1 whorled; gamosepalous, or polysepalous (on the hypanthium, often coloured inside); campanulate; regular; persistent (leathery); valvate. Corolla 4–8 (small); 1 whorled; polypetalous; crumpled in bud; regular.

Androecium (12–)16–100 (usually ‘many’). Androecial members branched, or unbranched; free of the perianth (on the hypanthium); free of one another, or coherent; when cohering, 4–8 adelphous (in clusters opposite the petals); 1–4 whorled (‘in clusters or in several whorls’). Androecium exclusively of fertile stamens. Stamens (12–)16–50; diplostemonous to polystemonous. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Anther wall initially with more than one middle layer (2 or 3); of the ‘dicot’ type. Tapetum glandular. Pollen grains aperturate; 3 aperturate; porate (Duabanga), or colporate (or colporoidate, Sonneratia); 2-celled.

Gynoecium 4–15 carpelled. Carpels isomerous with the perianth, or increased in number relative to the perianth. The pistil 4–15 celled. Gynoecium syncarpous; eu-syncarpous; superior to partly inferior (on a broad base). Ovary 4–15 locular. Styles 1 (bent in bud); from a depression at the top of the ovary; apical. Stigmas 1; capitate. Placentation axile. Ovules 10–50 per locule (‘many’); funicled; horizontal; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; very ephemeral. Synergids hooked. Endosperm formation nuclear. Embryogeny onagrad.

Fruit fleshy, or non-fleshy; indehiscent; a capsule, or a berry; 15–100 seeded (‘many’). Seeds non-endospermic. Cotyledons 2. Embryo chlorophyllous (1/1); straight, or curved.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Anatomy non-C4 type (Sonneratia). Sugars transported as sucrose (in Duabanga). Alkaloids absent (one species). Anthraquinones detected (Sonneratia); polyacetate derived. Saponins/sapogenins absent. Ellagic acid present.

Geography, cytology. Tropical. East tropical Africa and Madfagascar, Southeast Asia and Malaysia, Northern Australia, Western Pacific. X = 9, 18, 24.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Myrtales. Cronquist’s Subclass Rosidae; Myrtales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Myrtales (as a synonym of Lythraceae).

Species 7. Genera 2; Duabanga, Sonneratia.

General remarks. Apart from some differences in ‘esoteric charaters’ depending on limited sampling (mesophyll idioblasts, superficial cork cambium, libriform xylem fibres, chlorophyllous embryo, transported sugars comprising only sucrose), these compiled descriptions have Sonneratiaceae unimpressively distinguishable from Lythraceae (q.v.) only by the corolla aestivation and some variations in the androecium.

Illustrations. • Duabanga grandiflora (as D. sonneratioides): Hooker’s Illustrations of Himalayan plants (1855). • Sonneratia acida: Hutchinson. • Sonneratia caseolaris, as S. acida: Wight’s Figs. of Indian Plants 2 (1843).

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: 15th April 2018.’.