Autor: Britton & Rose 

Genus native to Matucana, a town near Lima, Peru, where the genus was first discovered.
A genus of low growing plants, solitary or caespitose, branching usually from the base, sometimes forming cushions. Stems globose, elongated to shortly cylindrical, with ribs very variable, low, more or less tuberculate; areoles bearing hairs and spines. Spines extremely variable according to species, numerous to few, often covering the epidermis of the plant, or simply absent.
Flowers diurnal, self-sterile, appearing near the apex, funnel-shaped with a more or less long floral tube with or without hairs, rarely actinomorphic (M. aureiflora, M. oreodoxa) or zygomorphic, intense red, orange, pink or yellow, pollinated by hummingbirds (Patagona gigas, Phaetornis spp.), but equally by bees. Fruits semi-globose to elongated, slightly fleshy, hollow, longitudinally dehiscent, floral remains persistent. Seeds variable, ovate either hood-shaped or helmet-shaped, blackish-brown, more or less shiny, ruminated or not, with a wide basal hilum, sometimes covered with the remains of the mucilage. Dispersion of seeds through myrmecochory and hydrochory.
The genus Matucana has extremely variable species, and grows endemically in the high valleys of the Andes in the North of Peru, mostly in full sun, in bare canyons, on cliffs, rocky hills, sometimes vertical slopes, often together with bromeliads, among grasses, mosses and lichens, and on rocky soils, from 280 m (M. paucicostata) up to 4200 m in altitude (M. comacephala).
Peru (Amazonas, Ancash, Arequipa, Ayacucho, Cajamarca, Huancavelica, Huanuco, Ica, Junin, La Libertad, Lima, Piura).

Currently 19 recognised species + 6 subspecies:
– Matucana aurantiaca* (Vaupel) Buxb. 1973
– Matucana aurantiaca subsp. currundayensis (F.Ritter) Mottram 1997
– Matucana aureiflora F.Ritter 1965
– Matucana formosa F.Ritter 1963
– Matucana fruticosa F.Ritter 1966
– Matucana hastifera F.Ritter 1981
– Matucana haynei* (Otto ex Salm-Dyck) Britton & Rose 1922
– Matucana haynei subsp. crinlfera (F.Ritter) Wittner 2012
– Matucana haynei subsp. herzogiana* (Backeb.) Mottram 1997
– Matucana haynei subsp. hystrix* (Rauh & Backeb.) Mottram 1997
– Matucana huagalensis (Donald & A.B.Lau) Bregman 1988
– Matucana intertexta* F.Ritter 1963
– Matucana krahnii (Donald) Bregman 1986
– Matucana madlsoniorum* (Hutchison) G.D.Rowley 1971
– Matucana myriacantha (Vaupel) Buxbaum 1973
– Matucana oreodoxa (F.Ritter) siaba 1986
– Matucana oreodoxa subsp. roseiflora G.Charles 2010
– Matucana paucicostata F.Ritter 1963
– Matucana paucicostata subsp. hoxeyi G.charles 2010
– Matucana polzii* Diers, Donald & Zecher 1986
– Matucana pujupatii (Donald & A.B.Lau) Bregman 1988
– Matucana rebutiiflora G.Charles 2013
– Matucana ritteri Burning 1959
– Matucana tuberculata (Donald) Bregman, Meerstadt, Melis & Pullen 1987
– Matucana weberbaueri (Vaupel) Backeb. 1939

References: "TAXONOMY of the CACTACEAE" -  ISBN 978-84-617-3692-8 (Vol. 2)