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The families of flowering plants

L. Watson and M.J. Dallwitz

Nepenthaceae Dum.

Including Pistiaceae C.A. Agardh (p.p.).

Habit and leaf form. Shrubs, or lianas, or herbs (mostly of boggy places, usually more or less woody). Plants carnivorous. Trapping mechanism passive. The traps consisting of ‘pitchers’ (holding water which houses rich communities of specialized small animals. The latter devour trapped insects, and nutritious excretions are absorbed by the plant through the pitcher walls. Chlorophyll-rich cells lining the pitcher serve to oxgenate the water, preventing it from becoming foetid). Perennial; without conspicuous aggregations of leaves. Epiphytic, or climbing, or epiphytic and climbing, or self supporting; mostly tendril climbers (the lamina midrib prolonged into a twining tendril, the tendril terminated by a pitcher). Mostly helophytic. Heterophyllous (sometimes with pitcher-bearing and non-pitcher-bearing leaves), or not heterophyllous. Leaves alternate; spiral; petiolate (the petiole winged); sheathing. Leaf sheaths tubular; with free margins. Leaves simple (at least, not ‘compound’ in the normal sense). Lamina entire; more or less linear (or strap-shaped); basically parallel-veined; cross-venulate. Leaves exstipulate. Lamina margins entire.

Leaf anatomy. Adaxial hypodermis present (aqueous). Minor leaf veins without phloem transfer cells (Nepenthes).

Axial (stem, wood) anatomy. Cork cambium present; initially deep-seated (the outer tissues being shed). Primary vascular tissues in a cylinder, without separate bundles to comprising a ring of bundles (comprising a ring of numerous, closely packed bundles); collateral. Internal phloem absent. Cortical bundles present (in the fibrous zones of young stems), or absent. Medullary bundles present (in some species), or absent. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls horizontal; simple. The axial xylem with tracheids; with fibre tracheids. ‘Included’ phloem absent.

Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Plants dioecious. Floral nectaries present. Nectar secretion from the perianth (from the tepals). Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, in racemes, and in panicles. The ultimate inflorescence units cymose, or racemose. Inflorescences terminal (but later overtopped by the branch from the uppermost leaf axil); racemes and thyrses. Flowers ebracteate; ebracteolate; small; fragrant; regular; cyclic. Hypogynous disk absent.

Perianth sepaline; (3–)4; free; 2 whorled (2+2, according to Airy Shaw); usually isomerous. Calyx (if the perianth regarded as such) (3–)4; 2 whorled; usually polysepalous, or gamosepalous (sometimes?). Degree of gamosepaly (maximum length joined/total calyx length) 2. Calyx regular; imbricate.

Androecium (2–)8–25. Androecial members free of the perianth; coherent; 1 adelphous (the filaments united into a column). Androecium exclusively of fertile stamens. Stamens (2–)8–25; isomerous with the perianth to polystemonous. Anthers dehiscing via longitudinal slits; extrorse; tetrasporangiate. Pollen shed in aggregates; in tetrads. Pollen grains indistinctly aperturate to nonaperturate; 2-celled.

Gynoecium (3–)4 carpelled. The pistil (3–)4 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary (3–)4 locular. Gynoecium non-stylate to stylate. Styles 1 (very short —the stigma almost sessile); very much shorter than the ovary. Stigmas 1; capitate to subpeltate; dry type; papillate; Group II type. Placentation axile (with many rows). Ovules 9–50 per locule (‘many’); ascending; non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating. Synergids pear-shaped.

Fruit non-fleshy (leathery); dehiscent; a capsule (elongated). Capsules loculicidal. Fruit 20–100 seeded (‘many’). Seeds endospermic. Endosperm oily (and starchy). Seeds filiform; winged (usually, with a narrow or hairlike wing at either end), or wingless (Aneurosperma). Seeds with starch. Embryo well differentiated (very short). Cotyledons 2; linear, plano-convex. Embryo straight (cylindrical).

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Not cyanogenic. Iridoids not detected. Betalains absent. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (2 species of Nepenthes). Aluminium accumulation not found.

Geography, cytology. Tropical. Seychelles, Indomalayan region, Madagascar, Ceylon, tropical Australia, New Caledonia.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Theiflorae; Theales. Cronquist’s Subclass Dilleniidae; Nepenthales. APG III core angiosperms; core eudicot; Superorder Caryophyllanae. APG IV Order Caryophyllales.

Species 68. Genera 2; Nepenthes, Anurosperma.

Illustrations. • Nepenthes macfarlanei: Hook. Ic. Pl. 29 (1906). • Nepenthes rafflesiana: Bot. Mag. 73 (1847). • Nepenthes villosa: Hook. Ic. Pl. 9 (1852). • Le Maout and Decaisne: Nepenthes. • Le Maout and Decaisne: Nepenthes. • Leaf hairs and glands of Nepenthes albomarginata and N. destillatoria (Solereder, 1908).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.