Rafflesiaceae Dumort.

Scientific Description

Common name. Rafflesia Family.

Habit and leaf form. Very peculiar endoparasitic herbs. Plants of very peculiar form; the vegetative parts filamentous, or fungoid. Leaves much reduced (at the bases of flowering stems, or beneath the flower), or absent. Plants rootless; totally parasitic (permeating the host tissues, with only the flowers or the flowering stems exserted). On roots of the host (mostly), or on aerial parts of the host (less often). Leaves alternate, or opposite, or whorled (usually); membranous (scales). Stem anatomy. Secondary thickening absent (the vascular system vestigial or absent).

Reproductive type, pollination. Fertile flowers hermaphrodite (rarely), or functionally male and functionally female, or functionally male, or functionally female. Unisexual flowers present (usually), or absent. Plants hermaphrodite (rarely), or monoecious, or dioecious. Entomophilous.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; small to very large (including Rafflesia arnoldii, with the largest known flowers — up to 1 m in diameter); malodorous (often), or odourless; regular; cyclic. Perianth sepaline, or petaline; 4, or 5(–10); 1 -whorled; free, or joined (often forming a tube); fleshy, or non-fleshy (usually imbricate, rarely valvate). Calyx (if the perianth so interpreted) 4, or 5(–10); 1 -whorled; polysepalous, or gamosepalous; imbricate (usually), or valvate (rarely); regular; fleshy (often, more or less), or non-fleshy. Fertile stamens present, or absent (in female flowers). Androecium of male flowers 5–100 (to ‘many’). Androecial members free of the perianth; united with the gynoecium (or at least, with the stylar column); free of one another (in 1–several cycles), or coherent (via the connate filaments, forming a tube round the stylar column); 1–4 -whorled (to ‘several’). Androecium exclusively of fertile stamens. Stamens 5–100 (to ‘many’); filantherous, or with sessile anthers. Anthers dehiscing via longitudinal slits (in the less modified forms), or dehiscing via pores, or dehiscing transversely; unilocular, or bilocular; tetrasporangiate. Pollen shed as single grains. Fertile gynoecium present, or absent (in male flowers). Gynoecium (in female flowers) 4–8 carpelled. The pistil 1 celled, or 3–10(–20) celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous (the stout, columnar style expanded into an often large, complex disk, with stigmatal projections); partly inferior, or inferior. Ovary variously, irregularly plurilocular, or unilocular; 1 locular, or 3–10(–20) locular (by deep intrusion of the placentas). Styles 1; apical. Placentation when unilocular, parietal (the placentas variously intruded or branched); when plurilocular, parietal (or with the ovules covering the inner surfaces of the partitions). Ovules in the single cavity 50–100 (‘very numerous’); 25–100 per locule (‘very numerous’); non-arillate; orthotropous (usually), or hemianatropous to anatropous.

Fruit and seed features. Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a berry, or a capsule. Capsules (when capsular) splitting irregularly. Gynoecia of adjoining flowers combining to form a multiple fruit, or not forming a multiple fruit. Seeds endospermic, or non-endospermic (Cytinus); minute. Embryo rudimentary at the time of seed release.

Geography, cytology, number of species. World distribution: South and Central America and Southwest U.S.A., Mediterranean and Middle East, Southern Africa and Madagascar, Southeast Asia and Malaysia, Australia. X = 12. 50 species.