Exostema

Exostema is a genus of flowering plants in the family Rubiaceae. It consists of trees and shrubs, endemic to the neotropics, with most of the species occurring in the West Indies.^[1][2]

Exostema
Illustration of Exostemma caribaeum
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Gentianales
Family:	Rubiaceae
Subfamily:	Cinchonoideae
Tribe:	Chiococceae
Genus:	Exostema (Pers.) Bonpl.
Type species
Exostema caribaeum (Jacq.) Schult.
Synonyms
Solenandra Hook.f. Steudelago Kuntze

Description

Exostema is a genus of neotropical trees and shrubs. The flowers have a slender corolla tube with recurved corolla lobes. The stamens are inserted near the base of the corolla tube and exserted well beyond its mouth. The anthers are long and basifixed.^[3]

Systematics

The type species for the genus is Exostema caribaeum.^[4] It is a tree of Central America and the Caribbean. Its lumber is of limited use.^[1]

Exostema was first named by Christiaan Hendrik Persoon as a subgenus of Cinchona.^[5] It was first validly published as a genus by Aimé Bonpland in 1807.^[6][7] The generic name is derived from the Ancient Greek words, exo, meaning "outside", and stema, "stamen".^[8]

As circumscribed in 2010, Exostema was probably polyphyletic.^[9] Species have since been moved to other genera.

Species

As of March 2023^[update], Plants of the World Online accepted the following species:^[10]

• Exostema acuminatum Urb.
• Exostema bicolor Poepp.
• Exostema caribaeum (Jacq.) Schult.
• Exostema coriaceum (Poir.) Schult.
• Exostema glaberrimum Borhidi & M.Fernández
• Exostema lancifolium Borhidi & Acuña
• Exostema nitens Urb.
• Exostema purpureum Griseb.
• Exostema revolutum Borhidi & M.Fernández
• Exostema salicifolium Griseb.
• Exostema spinosum (Le Vavass.) Krug & Urb.