The flowers are typically in a cymose inflorescence, with the perianth of the flowers united with the stamens to form a tube.
Nepenthaceae (pitcher plant family) is characterized by a relatively limited geographic range (Madagascar, Southeast Asia, Australia), shrubby to woody climbers, absence of petals, unisexual flowers and plants, stamens united into a column, flower clusters capable of growing terminally, a four-chambered ovary, and the formation of unique pitchers.
The unisexual flowers lack petals; male flowers have stamens united into a column, and female flowers have a four-chambered ovary.
In the tribe Bisboekelereae, the bracts below the terminal female flower are united to form a perigynium somewhat similar to that of the subfamily Caricoideae, though evolved independently.
Male and female parts of each flower are united in a single structure, and the pollen is characteristically massed in bundles called pollinia, pairs of which are linked by a yokelike bar of tissue contributed by the stigma of the pistil.
Flower: abaxial sepals united at base, scarious parts free; corolla lobes spreading, 1.3--2.8 mm, round-ovate, obtuse.
Flower: abaxial sepals united at base, scarious parts free; corolla lobes spreading (or 1 erect), 1.5--2 mm, ovate, +- acute.
Flower: sepals 5, united in basal 1/5, 1.5--10 1.5--10 1.5--10to ovate, glabrous to glandular-hairy; petals 5, 0.6--9 mm, entire; stamens 2--10; stylanceolate--1.9 mm.
Most members of Asclepiadoideae have milky juice, flowers with five united petals, podlike fruits, and, usually, tufted seeds.
One can hypothesize that there is a unique process of formation of synandria varying in intensity between flowers with partially united stamens to fully developed synandria.
The flowers have four or five united petals, which may be deeply divided.
