Cephalanthus

Cephalanthus is a genus of flowering plants in the family Rubiaceae. There are five extant species^[1] that are commonly known as buttonbush.^[3][4]

Cephalanthus
Cephalanthus occidentalis
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Gentianales
Family:	Rubiaceae
Subfamily:	Cinchonoideae
Tribe:	Naucleeae
Genus:	Cephalanthus L.[1]
Type species
Cephalanthus occidentalis L.[2]
Species[1]
Cephalanthus angustifolius Lour. Cephalanthus glabratus (Spreng.) K.Schum. Cephalanthus occidentalis L. Cephalanthus salicifolius Bonpl. Cephalanthus tetrandrus (Roxb.) Ridsdale & Bakh.f.
Synonyms[1]
Acrodryon Spreng. Axolus Raf. Eresimus Raf. Gilipus Raf. Silamnus Raf.

Description

They are shrubs or small trees growing to 5–15 m (16–49 ft) tall. The leaves are simple, arranged in opposite pairs or whorls of three. The flowers form a dense globular inflorescence.^{[citation needed]}

Distribution and habitat

Cephalanthus occidentalis is native to the eastern United States and Canada. The others occur in tropical regions of the Americas, Africa and Asia.^[5] Two species are known in cultivation.^[6]

Systematics

Cephalanthus was named by Linnaeus in Species Plantarum in 1753.^[7] The generic name is derived from the Ancient Greek words κέφαλη (kephale), meaning "head", and ἄνθος (anthos), meaning "flower".^[8]

Taxonomy

Cephalanthus is the most basal genus in the tribe Naucleeae.^[9] Some authors have segregated it into its own monotypic tribe.^[10] The type species is Cephalanthus occidentalis.^[11]

Species

The following five extant species are accepted:^[1][4][12]

• Cephalanthus angustifolius Lour. - Laos, Cambodia, Vietnam
• Cephalanthus glabratus (Spreng.) K.Schum. - sarandí - Brazil, Argentina, Paraguay, Uruguay
• Cephalanthus occidentalis L. - button-willow, common buttonbush, honey-bells - Cuba, eastern Canada, eastern, central and southern United States, California, Arizona, New Mexico
• Cephalanthus salicifolius Humb. & Bonpl. - Mexican buttonbush, willowleaf buttonbush - Mexico, Honduras, extreme southern tip of Texas
• Cephalanthus tetrandrus (Roxb.) Ridsdale & Bakh.f. - tropical Asia from India to China and Thailand

Fossil record

Sixteen fossil mericarps of †Cephalanthus pusillus have been described from middle Miocene strata of the Fasterholt area near Silkeborg in Central Jutland, Denmark.^[13]