Cephalanthus L. (Linnaeus 1753: 95)

Romero, Maria Florencia, Gonzalez, Ana Maria & Salas, Roberto Manuel, 2023, Sylvainia, a new monospecific genus within the subtribe Cephalanthinae (Rubiaceae, Naucleeae), Plant Ecology and Evolution 156 (1), pp. 85-111 : 85

Cephalanthus L. (Linnaeus 1753: 95)

Acrodryon Spreng. ( Sprengel 1824: 386) - Type species: Acrodryon angustifolium (Lour.) Spreng. (lectotype designated by Merrill 1935) [= Cephalanthus angustifolius Lour.].

Axolus Raf. ( Rafinesque 1838: 61) - Type species: Axolus angustifolius (Lour.) Raf. [= Cephalanthus angustifolius Lour.].

Eresimus Raf. ( Rafinesque 1838: 60) - Type species: Cephalanthus stellatus Lour. [= Cephalanthus angustifolius Lour.].

Type species.

Cephalanthus occidentalis L. (lectotype designated by Merrill 1915).

Description.

Shrubs or small trees 3-5 m tall, much-branched. Stems with lenticels, fragile. Leaves opposite or verticillate, pseudopetiolate; blades narrowly elliptical, oblong to narrowly ovate, glabrous to pubescent, discolorous; veins slightly discolorous; leaf domatia generally present on the abaxial side; stipules interpetiolar, tardily deciduous, with dark colleters at the apex and along the margin, and light colleters on the ventral (inner) side, near the base. Inflorescences terminal and axillary, thyrsoid, cymose, in pleiochasium, bracteose or frondobracteose, partial inflorescences in glomeruli, strongly congested, spherical, pedunculate, with synchronic anthesis; bracteoles spatulate, with dark colleters, pubescent. Flowers perfect or morphologically perfect, but functionally imperfect in C. glabratus , actinomorphic, sessile; calyx 4- or 5-lobed; corolla infundibuliform or hypocrateriform, 4- or 5-lobed; imbricated in bud; lobes rounded, internally pubescent or glabrous, externally with dark colleters at the interlobular sinuses; tube internally with a fringe of hairs or glabrous, externally glabrous; stamens 4 or 5, with filiform filaments, glabrous; anthers subsessile; hypanthium cupuliform, obovate or turbinate; ovary 2-carpellate, 2-locular, each locule 1-ovulate; ovules pendulous; style filiform; stigma capitate or shortly bilobate, exserted at the end of anthesis. Fruit a schizocarp, glabrous or pubescent; pericarp coriaceous and thin; seeds flat-convex, sub-rhomboid in outline, fragile, with surface almost smooth, microscopically papillose; aril prominent, dorsal, longer than the seed length, white, softly rough, and spongy.

Distribution.

Pantropical, 6 species: 3 from the Americas and 3 from tropical Asia.