Tropical pitcher plant (Nepenthes sibuyanensis)

Description

Nepenthes sibuyanensis /nɪˈpɛnθiːz sɪˈbʊjənɛnsɪs/ is a tropical pitcher plant endemic to Sibuyan Island in the Philippines, after which it is named. Nepenthes sibuyanensis is a weak climber. The stem can attain a length of 1.5 m and is up to 8 mm in diameter. Internodes are up to 1.5 cm long and cylindrical in cross section. Leaves are thin-coriaceous and sessile. The lamina is linear-lanceolate to slightly spathulate in shape. It may be up to 18 cm long and 5 cm wide. The lamina has an acute apex and is gradually attenuate towards the base. It is decurrent into a pair of margins that extend for over two-thirds of the internode. Five to six longitudinal veins are present on either side of the midrib. Tendrils are usually one to two times as long as the pitchers and up to 9 mm wide near the pitcher. Pitchers arise from the end of the tendril, forming a tightly appressed curve. Lower pitchers are ovate to infundibuliform in shape and may be up to 26 cm high and 15 cm wide. A pair of ribs runs down the front of the pitcher, sometimes bearing fringe elements (≤3 mm wide) near the peristome. The pitcher mouth is oval and has an almost horizontal to slightly oblique insertion. The peristome is cylindrical, usually elongated into a short neck, and up to 20 mm wide. It bears a series of ribs (≤1 mm high) spaced 2 mm apart. The teeth lining the inner margin of the peristome are up to 4 mm long. The inner portion of the peristome accounts for around 54% of its total cross-sectional surface length. The glandular region covers the entire inner surface of the pitchers; there is no waxy zone. The glands are up to 0.8 mm in diameter and occur at a density of 200 to 500 per square centimetre. The lid or operculum is broadly ovate-cordate and up to 8 cm long and 6.5 cm wide. It has a rounded apex and lacks appendages. A number of ovate glands (≤1 mm in diameter) are concentrated near the centre of the lid's lower surface. A filiform spur (≤3 mm long) is inserted near the base of the lid. Upper pitchers are very rarely produced. They are generally smaller and lighter-coloured than their terrestrial counterparts. Nepenthes sibuyanensis has a racemose inflorescence. In male inflorescences, the peduncle reaches a length of at least 18 cm, whereas the rachis is up to 15 cm long. Pedicels are one-flowered, up to 14 mm long, and usually lack bracts. Tepals are oblong, obtuse, and approximately 3 mm long. Stamens are around 5 mm long including the uniseriate anthers. Fruits are up to 22 mm long and bear lanceolate valves (≤4 mm wide). Seeds are up to 8 mm long and filiform, although they lack the papery ends typical of most Nepenthes species. The inflorescence bears a very dense indumentum of adpressed, stellate hairs. The staminal column is covered in short hairs. Vegetative parts of the plant are virtually glabrous. Leaves are yellowish to dark green with a light green midrib. The stem and leaf margins may have reddish highlights. Lower pitchers are yellowish to red, often with scattered red blotches (≤10 mm in diameter) below the peristome. The peristome is usually darker than the rest of the pitcher, being dark red to almost black. The lid is yellowish to orange. Upper pitchers are lighter-coloured and usually whitish throughout. Herbarium specimens range in colour from light brown to red.