Family Rhabdodendraceae

Rhabdodendraceae (Engl.) Prance

~ Rutaceae p.p.

Habit and leaf form. Tall, fastigiate or subpyramidal shrubs. Leaves alternate; leathery; gland-dotted; simple. Lamina entire. Leaves stipulate, or exstipulate. Stipules if present, caducous.

Leaf anatomy. Stomata present; anomocytic. Hairs present. Complex hairs present; peltate (short-stalked, with siliceous inclusions).

Lamina with secretory cavities (also with scattered fatty bodies). Secretory cavities containing resin; lysigenous. The mesophyll with sclerencymatous idioblasts (traversed by fibre-like, simple or branched sclereids representing prolongations from the vein ends, and many of the mesophyll cells with silicified walls).

Stem anatomy. Nodes multilacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring, or anomalous; via concentric cambia, or from a single cambial ring. ‘Included’ phloem present. Xylem with vessels. Vessel end-walls simple. Wood parenchyma largely apotracheal, or paratracheal (then very scanty-diffuse). Sieve-tube plastids P-type; type I (b).

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in racemes. The ultimate inflorescence unit cymose, or racemose. Inflorescences axillary (or supra-axillary); racemes, or racemelike cymes with terminal flowers. Flowers regular; cyclic; polycyclic (by virtue of the androecium). Free hypanthium present (short, the flowers slightly perigynous). Hypogynous disk absent.

Perianth with distinct calyx and corolla; 10 (or the calyx more or less entire); 2 whorled. Calyx basically 5 (but the lobes short or obscure); 1 whorled; gamosepalous; five lobulate to blunt-lobed, or entire; regular; imbricate (when lobed), or open in bud. Corolla 5 (sepal-like); 1 whorled; polypetalous (the petals glandular-punctate); imbricate and valvate (slightly imbricate below and valvate above, or cochlear); regular; deciduous (caducous).

Androecium 25–50. Androecial members when the stamens not developing more or less simultaneously, weakly maturing centripetally; free of the perianth; free of one another; more or less 3 whorled. Androecium exclusively of fertile stamens. Stamens 25–50; polystemonous; erect in bud; shortly filantherous (the filaments flattened, persistent). Anthers basifixed (elongated, apically emarginate, caducous); non-versatile; dehiscing via longitudinal slits; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3(–4) aperturate; colporate; 3-celled.

Gynoecium 1 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium monomerous; of one carpel; superior. Carpel stylate; with a gynobasic style (the style thick, virtually basal, externally stigmatic for half to all of its length); 1(–2) ovuled (the second, if present, abortive). Placentation basal. Ovules epitropous; orthotropous, or hemianatropous; unitegmic.

Fruit scarcely fleshy, or non-fleshy. The fruiting carpel indehiscent; drupaceous (globular, borne on the woody pedicel and shortly stipitate within the cupular hypanthium, the exocarp thin and eventually crustaceous, the endocarp slightly woody). Fruit 1 seeded. Seeds non-endospermic. Embryo well differentiated. Cotyledons 2 (thick, fleshy). Embryo bent (the radicle bent inwards towards the hilum).

Physiology, biochemistry. Cyanogenic.

Geography, cytology. Neotropical. Tropical. North Brazil, Guianas. X = 10.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae (? — reassigned on the basis of rbcL sequencing, Chase et al. 1993); near Caryophyllales (?). Cronquist’s Subclass Rosidae; Rosales. APG 3 core angiosperms; core eudicot; Superorder Caryophyllanae; Order Caryophyllales.

Species 4. Genera 1; only genus, Rhabdodendron.