Rhynchocalycaceae Johnson and 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.
Stem anatomy. Young stems cylindrical, or flattened. Nodes unilacunar (with one trace). Secondary thickening developing from a conventional cambial ring. Xylem without fibre tracheids; with libriform fibres (septate). Vessel end-walls oblique; simple. Vessels with vestured pits. Wood parenchyma scanty paratracheal (to vasicentric).
Reproductive type, pollination. 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 straight (apical).
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 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Myrtales (as a synonym of Penaeaceae?).
Species 1. Genera 1; only genus, Rhynchocalyx.
This rather inadequate description is expanded from the brief Latin diagnosis of Johnson and Briggs with reference to Graham (1984), Hiroshi and Raven, P.H. (1984) and standard works.