Family Nepenthaceae
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; with neither basal nor terminal 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). Stem anatomy. Cork cambium present; initially deep-seated. Primary vascular tissue comprising a ring of bundles. Cortical bundles present, or absent. Medullary bundles present, or absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids; with vessels. Vessel end-walls horizontal; simple. 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 unit 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, biochemistry. Not cyanogenic. Iridoids not detected. 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 3 core angiosperms; core eudicot; Superorder Caryophyllanae; Order Caryophyllales. Species 68. Genera 2; Nepenthes, Anurosperma. Illustrations. |
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