| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Rhynchocalycaceae Johnson & Briggs

~ Crypteroniaceae, Penaeaceae.

Habit and leaf form. Small trees. Mesophytic. Leaves opposite (decussate), or whorled; petiolate; simple. Lamina entire; eucamptodromous. Leaves stipulate. Stipules intrapetiolar (axillary, ‘divided’).

Leaf anatomy. Stomata present; anomocytic. The mesophyll without sclerenchymatous idioblasts.

Axial (stem, wood) anatomy. Young stems cylindrical, or flattened. Nodes unilacunar (with one trace). Secondary thickening developing from a conventional cambial ring.

The vessel end-walls oblique; simple. The vessels with vestured pits. The axial xylem without fibre tracheids; with libriform fibres; including septate fibres. The parenchyma scanty paratracheal (to vasicentric).

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

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. Inflorescences terminal and axillary; anthotelic panicles. Flowers regular; 6 merous. Free hypanthium present. Hypogynous disk absent.

Perianth with distinct calyx and corolla; 12; 2 whorled. Calyx 6; 1 whorled; persistent (membranous); valvate. Corolla 6; 1 whorled; polypetalous; deciduous. Petals clawed (hoodlike, covering the stamens in bud).

Androecium 6. Androecial members free of the perianth (inserted in the mouth of the hypanthium); free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 6; isomerous with the perianth; alternisepalous; opposite the corolla members; initially incurved; filantherous (the filaments long, more or less flattened). Anthers dorsifixed to basifixed (the connective elliptical); bilocular (the sporangia lateral); tetrasporangiate. Endothecium ephemeral. Anther wall initially with more than one middle layer (2); of the ‘basic’ type. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 6 aperturate; colpate and colporate (tricolporate, with three subsidiary colpi); 2-celled.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil (1–)2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary (1–)2 locular (bilateral, compressed). Gynoecium stylate. Styles 1; apical; shorter than the ovary (stout, the base persistent). Stigmas 1; capitate (narrow). Placentation axile. Ovules 20–100 per locule (‘many’, or ‘about 40’); horizontal; anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Endosperm formation nuclear. Embryogeny onagrad.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Seeds non-endospermic; obliquely ovate, flattened; winged (at the micropylar end). Cotyledons 2. Embryo apical, straight.

Geography, cytology. Cape. Sub-tropical. Southern Africa (Natal and Transkei).

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 Penaeaceae?).

Species 1 (Rhynchocalyx lawsonioides). Genera 1; only genus, Rhynchocalyx.

General remarks. This rather inadequate description is compiled from the brief Latin diagnosis of Johnson and Briggs with reference to Graham (1984), Hiroshi and Raven, P.H. (1984) and standard works. It is readily distinguishable from those of Crypteroniaceae and Penaeaceae (q.v.) in assorted, conspicuous general morphological characters, as well as in some ‘esoteric’ characters depending on restricted sampling, but is indistinguishable from that of Lythraceae sensu stricto (q.v.) save in anther wall formation type (another character relying on limited sampling).

Illustrations. • Rhynchocalyx lawsonioides: Hook. Ic. Pl. 24 (1895).

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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