| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Sphaerosepalaceae Van Tiegh.

Alternatively Rhopalocarpaceae Hemsl.

Habit and leaf form. Trees, or ‘arborescent’, or shrubs. Leaves deciduous; alternate; simple. Lamina entire; pinnately veined, or palmately veined (then three veined). Leaves stipulate. Stipules intrapetiolar; large, caducous.

Leaf anatomy. Stomata present; anomocytic, or anisocytic, or cyclocytic. The mesophyll containing mucilage cells.

Axial (stem, wood) anatomy. Internal phloem absent. Cortical bundles absent. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls simple. The vessels without vestured pits. The axial xylem with tracheids. ‘Included’ phloem absent. The wood partially storied (VP, Rhopalocarpus).

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’. The ultimate inflorescence units cymose. Inflorescences terminal, or axillary; subumbelliform cymules. Flowers bracteate (each flower subtended by several caducous bracts); regular to somewhat irregular; polycyclic. Free hypanthium absent. Hypogynous disk present; intrastaminal; annular (large, ‘gynophore-like’, wrinkled, denticulate).

Perianth with distinct calyx and corolla; (7–)8(–10); 3 whorled, or 4 whorled (?); isomerous. Calyx 4, or 6; 2 whorled (2+2, rarely 3+3); polysepalous (the innermost larger); not persistent (caducous, leathery); strongly imbricate. Corolla (3–)4(–8); polypetalous; imbricate (the petals unequal, densely streaked with short, resinous lines); white, or yellow; deciduous (caducous). Petals slightly clawed.

Androecium 25–100 (or more). Androecial members maturing centrifugally; free of the perianth; markedly unequal (the outer filaments shorter); irregularly coherent, or free of one another; usually shortly and irregularly connate at the base into groups; 2–4 whorled (in series). Androecium exclusively of fertile stamens. Stamens 25–100 (or more); polystemonous; filantherous. Anthers dehiscing via longitudinal slits; bilocular (the locules widely separated, the connective broad and glandular); tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3–7 aperturate; colporate (colporoidate).

Gynoecium (2–)3(–5) carpelled. The pistil (2–)4(–5) celled. Gynoecium syncarpous; synstylous (Dialyceras, with the carpels free save for a common gynobasic style), or eu-syncarpous (Rhopalocarpus, with a single geniculate style and an entire stigma); superior, or superior to partly inferior (partially sunken in the disk). Carpel of Dialyceras, with free ovaries, 2–9 ovuled. Placentation marginal, or basal. Ovary (2–)4(–5) locular (as many as the carpels, but the ‘locules’ separate in Dialyceras). Gynoecium stylate. Styles 1; from a depression at the top of the ovary; apical, or ‘gynobasic’ (in Dialyceras). Placentation basal to axile (in Rhopalocarpus, but ‘marginal to basal’ in the free locules of Dialyceras). Ovules 2–9 per locule; ascending; anatropous.

Fruit an aggregate, or not an aggregate; indehiscent (Rhopalocarpus), or a schizocarp (Dialyceras). Mericarps in Dialyceras, (2–)3(–5); of Dialyceras with 1(-2) large seeds. Fruit of Rhopalocarpus capsular-indehiscent (globose or lobed according to the number of carpels, densely muricate); 4–10 seeded (1(-2) per locule). Seeds endospermic. Endosperm ruminate; oily. Seeds large. Embryo well differentiated (but rather small). Cotyledons 2 (bilobed, sometimes ruminate). Embryo straight.

Physiology, phytochemistry. Ellagic acid present.

Geography, cytology. Paleotropical. Tropical. Madagascar.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Malvales. Cronquist’s Subclass Dilleniidae; Theales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Malvales.

Species 14. Genera 2; Rhopalocarpus (Sphaerosepalum), Dialyceras.

Illustrations. • Rhopalocarpus lucidus: Hook. Ic. Pl. 28 (1903). • Rhopalocarpus alternifolius: Hutchinson. • Dialyceras parvifolium: Capuron, in Fl. Madag. (1963).

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: 8th June 2026. delta-intkey.com’.

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