Autor: Britton & Rose

A genus dedicated to Dr. Miguel Arrojado Lisboa (1872-1932), superintendent of the Brazilian Railroads at the time Britton & Rose described the genus in his honor in 1920. His portrait is unknown, the photo above represents an old Brazilian station that bears his name (©Newton Viana Leite).
Genus with solitary or branched stems appearing from the base, more or less slender, erect or pendulous, sometimes rhizomatous. Areoles usually close each other, spines rather small, often setose.
Flowers diurnal, self sterile, tubular, apical, naked, emerging from an annular cephalium, red, pink, purple, yellow, sometimes white, pollinated by hummingbirds (Chlorostilbon lucidus, Phaethornis pretrei, Eupetomena macroura).
Fruits spherical to pyrlform, juicy, indehiscent. Seeds shiny, black, tuberculate. Dispersal is essentially ornithophilous.
The genus Arrojadoa grows in the caatinga, the spiny dry forest of the northeastern (nordeste) of Brazil, from 270 m up to approximately 1100 m in altitude, among bushes which serve as support for the larger species of the genus, in the shade under shrubs, on soils slightly loamy and sandy, quartz gravel or manganesiferous altered soils, together with other Cactaceae as well as terrestrial bromeliads.
Brazil (Bahia, Minas Gerais, Pernambuco, Piaui).

Currently 9 recognised species + three subspecies:
– Arrojadoa x albiflora Buining & Brederoo 1975 (= A. dinae x A. rhodantha)
– Arrojadoa beateae P.J.Braun & Esteves 1989 (= A. heimenii)
– Arrojadoa dinae Buining & Brederoo 1973
– Arrojadoa eriocaulis Buining & Brederoo 1973
– Arrojadoa eriocaulis subsp. nana (P.J.Braun & Esteves) P.J.Braun & Esteves 1995
– Arrojadoa horstiana P.J.Braun & G.Heimen 1981
– Arrojadoa marylanae Soares Filho & Machado 2003
– Arrojadoa multiflora Ritter 1979
– Arrojadoa penicillata* (Gürke) Britton & Rose 1920
– Arrojadoa rhodantha* (Gürke) Britton & Rose 1920
– Arrojadoa rhodantha subsp. aureispina (Buining & Brederoo) P.J.Braun & Esteves 1995
– Arrojadoa rhodantha subsp. reflexa P. J. Braun 1984


References: "TAXONOMY of the CACTACEAE" -  ISBN 978-84-617-3723-9 (Vol. 1)