Nepenthes ( nih-PEN-theez) is a genus of carnivorous plants, also known as tropical pitcher plants, or monkey cups, in the monotypic family Nepenthaceae. The genus includes about 170 species, and numerous natural and many cultivated hybrids. They are mostly liana-forming plants of the Old World tropics, ranging from South China, Indonesia, Malaysia, and the Philippines; westward to Madagascar (two species) and the Seychelles (one); southward to Australia (four) and New Caledonia (one); and northward to India (one) and Sri Lanka (one). The greatest diversity occurs on Borneo, Sumatra, and the Philippines, with many endemic species. Many are plants of hot, humid, lowland areas, but most are tropical, montane plants, receiving warm days but cool to cold, humid nights year-round. A few are considered tropical alpine, with cool days and nights near freezing. The name "monkey cups" refers to the fact that monkeys were once thought to drink rainwater from the pitchers.
Description
Nepenthes species usually consist of a shallow root system and a prostrate or climbing stem, often several metres long and up to 15 m (49 ft) or more, and usually 1 cm (0.4 in) or less in diameter, although this may be thicker in a few species (e.g. N. bicalcarata). From the stems arise alternate, sword-shaped leaves with entire leaf margins. An extension of the midrib (the tendril), which in some species aids in climbing, protrudes from the tip of the leaf; at the end of the tendril the pitcher forms. The pitcher starts as a small bud and gradually expands into a globe- or tube-shaped trap.
The trap contains a fluid secreted by the plant, which may be watery or more viscous, and is used to drown the prey. This fluid contains viscoelastic biopolymers that may be crucial to the retention of insects within the traps of many species. The viscoelastic fluid in the pitchers is effective in the retention of winged insects. The trapping efficiency of this fluid remains high, even when significantly diluted by water, as inevitably happens in wet conditions. The lower part of the trap contains glands that absorb nutrients from captured prey. Along the upper inside part of the trap is a slick, waxy coating, which makes the escape of its prey nearly impossible. Surrounding the entrance to the trap is a structure called the peristome (the "lip"), which is slippery and often quite colourful, attracting prey, but offering an unsure footing. The prey-capture effectiveness of the peristome is further enhanced in moist environments, where condensation may cause a thin water film to form on the surface of the peristome. When wet, the slippery surface of the peristome causes insects to "aquaplane", or slip and fall, into the pitcher. Above the peristome is a lid (the operculum); in many species, this keeps rain from diluting the fluid within the pitcher, the underside of which may contain nectar glands that attract prey. Nepenthes species usually produce two types of pitchers, known as leaf dimorphism. Appearing near the base of the plant are the large, lower traps, which typically sit on the ground. The upper or aerial pitchers are usually smaller, coloured differently, and possess different features from the lower pitchers. These upper pitchers usually form as the plant reaches maturity and the plant grows taller. To keep the plant steady, the upper pitchers often form a loop in the tendril, allowing it to wrap around nearby support. In some species (e.g. N. rafflesiana), different prey may be attracted by the two types of pitchers. This varied morphology also often makes identification of species difficult. Prey usually consists of insects, but the largest species (e.g. N. rajah and N. rafflesiana) may occasionally catch small vertebrates, such as "frogs, birds, and small mammals". Records of cultivated plants trapping small birds have been made. Flowers occur in racemes or more rarely in panicles with male and female flowers on separate plants. Three species have symbiotic relationships with treeshrews, which eat the nectar produced by the plant and defecate into the pitchers, providing valuable nutrients. Nepenthes are insect-pollinated, the primary agents being flies (including blow flies, midges, and mosquitoes), moths, wasps, and butterflies. Their smells can range from sweet to musty or fungus-like. Seed is typically produced in a four-sided capsule which may contain 50–500 wind-distributed seeds, consisting of a central embryo and two wings, one on either side (though N. pervillei differs). The genus is cytologically diploid, with all studied species having a chromosome number of 2n=80. This high number is thought to reflect paleopolyploidy (likely 8x or 16x).
Taxonomy
About 170 species of Nepenthes are currently recognised as valid. This number is increasing, with several new species being described each year.
Etymology The genus name Nepenthes was first published in 1737 in Carl Linnaeus's Hortus Cliffortianus. It references a passage in Homer's Odyssey, in which the potion "Nepenthes pharmakon" is given to Helen by an Egyptian queen. "Nepenthes" (Ancient Greek: νηπενθές) literally means "without grief" (νη nē = "not", πένθος penthos = "grief") and, in Greek mythology, is a drug that quells all sorrows with forgetfulness. Linnaeus explained:
If this is not Helen's Nepenthes, it certainly will be for all botanists. What botanist would not be filled with admiration if, after a long journey, he should find this wonderful plant. In his astonishment, past ills would be forgotten when beholding this admirable work of the Creator! [translated from Latin by Harry Veitch] The plant Linnaeus described was N. distillatoria, called bāndurā (බාඳුරා), a species from Sri Lanka. Nepenthes was formally published as a generic name in 1753 in Linnaeus's famous Species Plantarum, which established botanical nomenclature as it exists today. Nepenthes distillatoria is the type species of the genus.
The name "monkey cups" was discussed in the May 1964 issue of National Geographic, in which Paul A. Zahl wrote:
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