Family Roridulaceae

Roridulaceae Engl. & Gilg

~ Byblidaceae

Habit and leaf form. Small shrubs (shrublets). Plants curiously, indirectly ‘carnivorous’. Trapping mechanism passive. The traps consisting of the sticky-glandular, non-irritable (flypaper-like) leaves (with stalked, capitate, viscous-glandular tentacles of various lengths. The sticky exudate entraps insects, but contains no digestive enzymes: the captives are eaten by a specialized hemipteran bug, whose nutritious excretions are absorbed by the plant through its leaves (Ellis and Midgely 1996, Oecologia 106, 478)). Leaves alternate; simple. Lamina dissected, or entire; linear to lanceolate; when dissected, pinnatifid. Leaves exstipulate. Vernation circinnate; circinnate.

Leaf anatomy. Stomata present; anomocytic.

Lamina dorsiventral.

Stem anatomy. Secondary thickening developing from a conventional cambial ring (?). Vessel end-walls scalariform. Primary medullary rays narrow (mostly uniseriate). Wood parenchyma apotracheal.

Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous; by small Heteroptera; mechanism conspicuously specialized (the sensitive stamens springing suddenly upright to scatter pollen over visiting insects).

Inflorescence, floral, fruit and seed morphology. Flowers solitary (axillary, according to Airy Shaw 1973), or aggregated in ‘inflorescences’ (in terminal racemes, according to Cronquist); if solitary, axillary; (bi-) bracteolate; regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; gamosepalous (basally connate); blunt-lobed, or toothed; regular; persistent; imbricate. Corolla 5; 1 whorled; gamopetalous (shortly connate basally). Corolla lobes markedly longer than the tube. Corolla imbricate; regular (the lobes broad-elliptic, acute).

Androecium 5. Androecial members adnate (to the base of the corolla); all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members; inflexed in bud; filantherous. Filaments thickened at the base. Anthers basifixed; becoming inverted during development, their morphological bases ostensibly apical in the mature stamens; apically dehiscing via pores, or dehiscing via short slits; extrorse; bilocular; tetrasporangiate. Pollen grains aperturate; 3 aperturate; sulculate (colporoidate).

Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 3 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 3 locular; sessile. Gynoecium shortly stylate. Styles 1; apical. Stigmas 1; capitate. Placentation axile to apical. Ovules 1–6 per locule (to ‘several’); pendulous; anatropous; unitegmic, or bitegmic; tenuinucellate.

Fruit non-fleshy; dehiscent; a capsule. Capsules septicidal and loculicidal (the three loculicidal and semiseptiferous valves separated from the persistent columella). Seeds copiously endospermic (the endosperm fleshy); medium sized to large (‘rather large’); with a testa (this crustaceous, areolate). Embryo well differentiated (but small). Cotyledons 2. Embryo straight.

Seedling. Germination phanerocotylar.

Physiology, biochemistry. Not cyanogenic. Iridoids detected; ‘Route I’ type (+seco). Proanthocyanidins absent.

Geography, cytology. Cape. Sub-tropical to tropical. South Africa.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Ericales. Cronquist’s Subclass Rosidae; Rosales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Ericales.

Species 2. Genera 1; only genus, Roridula.

These data on ‘tentacular glands’ (hairs or enations?), embryology etc. are inadequate — Lloyd not yet consulted).