Drosera L.

Scientific Description

Common name. Sundews. Family Droseraceae.

Habit and leaf form. Lianas, or herbs. Plants with roots; ‘carnivorous’. Trapping mechanism active. The traps consisting of the sticky-glandular, non-irritable (flypaper-like) leaves. Annual, or perennial (or sometimes ephemeral). Leaves basal, or cauline, or basal and cauline. Plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Stem internodes solid (ass.). Rhizomatous, or tuberous. Helophytic to mesophytic (usually in acid bogs). Leaves small to medium-sized; alternate; spiral, or four-ranked; petiolate, or sessile; non-sheathing; simple. Leaf blades entire. Leaves with stipules (scarious), or without stipules; without a persistent basal meristem. Vernation often circinnate; circinnate, or not circinnate. Leaf anatomy. Hairs present, or absent (rarely); glandular hairs present (adaxial surface or whole lamina covered with glandular trichomes which trap insects). Stem anatomy. Secondary thickening absent.

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

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in cymes (forked), or in racemes (1-sided). The terminal inflorescence unit cymose (usually), or racemose. Inflorescences terminal, or axillary (or lateral or radicle); usually cincinni. Flowers bracteate (ass.), or ebracteate (few to numerous prophylls sometimed present on base of aerial and underground stems); regular; usually 4–5 merous; cyclic; tetracyclic, or pentacyclic. Free hypanthium present (slight), or absent. Hypogynous disk absent. Perianth with distinct calyx and corolla; 8–10(–16); 2 -whorled; isomerous. Calyx present; (4–)5(–8); 1 -whorled; polysepalous, or gamosepalous (shortly united at base); imbricate; regular; persistent (marcescent). Corolla present; (4–)5, or 8(–12); 1 -whorled; polypetalous; imbricate, or contorted; regular. Petals obovate (to spathulate); shortly clawed. Corolla members bilobed (convolute). Androecial members definite in number. Androecium 4–5, or 8–12. Androecial members branched, or unbranched; free of the perianth; all equal (ass.); free of one another; 1 -whorled, or 2 -whorled. Androecium exclusively of fertile stamens. Stamens 4–5, or 8–12; all more or less similar in shape (ass.); isomerous with the perianth to triplostemonous; oppositisepalous. Anthers dorsifixed, or basifixed; dehiscing via longitudinal slits; extrorse; tetrasporangiate. Pollen shed in aggregates; usually in tetrads. Gynoecium 3(–5) carpelled. The pistil 1 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary unilocular; 1 locular. The ‘odd’ carpel when G3 posterior. Ovary sessile (ass.). Gynoecium stylate. Styles 3–5; free, or partially joined; apical. Stigmas often 2 - lobed. Placentation parietal, or basal. Ovules in the single cavity 20–50 (many); ascending; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal, or valvular. Fruit 20–100 seeded (numerous or several). Seeds copiously endospermic. Endosperm oily. Embryo well differentiated (small). Cotyledons 2. Embryo straight.

Etymology. From the Greek for "dewy"; refers to the prominent glandular hairs, which give the plant the appearance of being covered with dew.