Nepenthes are herbaceous perennials whose stems are quite coarse, having diameters exceeding 2 in. (5 cm). In some species the length of the stem exceeds 66 ft. (20 m). The stems either climb on nearby bushes and trees or are prostrate, creeping on the ground. Arising from the stems, which vary in cross section from circular to triangular are the long narrow leaves which in some species are over 2 ft. (.6 m) in length. (Fig. 3-9)
The fluid of unopened pitchers has been used as a laxative, a remedy for burns, coughs, inflamed eyes and various skin disorders. Open pitchers are used to carry water and as pots for cooking food, while the vines are used for cordage. Pitcher color varies from shades of green to yellow with red and/or purple variegation.
The long leaf blades are green to yellow-green with midribs that extend beyond the leaf blade apex to form a cylindrical tendril which is as long or longer than the leaf blade. The tips of the yellow-green tendrils develop into pitchers in an appropriate environment.
Nepenthes plants tend to have two types of pitchers. While pitcher shape varies with the species, generally pitchers close to the ground are cylindrical with two parallel wings extending from the top to bottom on the front of the pitcher. Pitchers on the upper parts of the plant are roughly funnel-shape, tapering toward the tendril end. These tendrils coil around adjacent structures and plants to provide the means of support. The tendrils supporting the lower pitchers do not coil.
The mouth of the opening to the pitcher is edged with a ridged collar, the peristome. The ridges in the peristome terminate in sharp points on the inner side of the pitcher. They are believed to aid in preventing escape by presenting a barrier to prey trying to climb out of the pitcher.
Fig. 3-9 Nepenthes plant with inforescence, upper and lower leaves with traps.
Overhanging the mouth of the pitcher is a lid whose size varies considerably between species. The lid is attached to the back side of the pitcher orifice. It separates from the front of the pitcher as the pitcher matures, forming a flap or hood over the mouth which in some species prevents water from entering the pitcher. (Fig. 3-10) It was once erroneously believed that the lid was capable of motion and involved in trapping prey. Protruding from the area of attachment of the lid to the pitcher body is a finger-like projection called a spur. Pitcher color varies from green to green mottled with deep red or purple.
Nepenthes plants are dioecious. Therefore, to produce seed two plants are needed, one bearing male flowers and the other female flowers. Neither male nor female flowers are showy. They are small, lack petals, have four sepals, and their reproductive structures, either stamens or pistils, are located centrally in the flower and look quite similar to each other. Female flowers can be distinguished by the swollen superior ovary just above the sepals. The flowers are borne in panicles or racemes. (Photo 3-6)
The glands producing nectar are found at the base of each inner projection of the peristome and the inner surface of the lid. Capture occurs when prey, feeding on the nectar near the opening of the pitcher, slips and falls into the liquid bath in the trap. (Photo 3-7) The viscosity of the digestive fluid, a mixture of rain water and enzymes, combined with the sharp peristomes tend to prevent the prey from escaping. The struggling prey is reportedly tranquilized by an unidentified agent in the liquid.
Digestive and absorbing glands are located in the lower, inside walls of the pitchers. Digestive enzymes are secreted into the liquid that accumulates in the pitcher. Bacterial decomposition aids the digestive enzymes in the breakdown of the captured prey.
Nepenthes plants possess the largest trap of any of the carnivorous genera. Nepenthes merrilliana from the Philippines produces the largest pitchers exceeding 20 in. (50 cm) in length and 10 in. (25 cm) in diameter. Allegedly, small birds, rats and other such animals have been caught by the pitchers, which are locally known by a variety of names such as Monkey Pitchers and Monkey's Rice Pots.
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