Autor: Link & Otto

≪Melon cactus≫, referring to the globular shape characteristic of most species within the genus.
A genus of solitary plants (however being able to make clusters close to the cephalium if the apex has been damaged, or if the base of the cephalium is attacked by mealybugs), globose, elongated to cylindrical, with the apex depressed when juvenile. Ribs variable in number (8-27), well defined, not tuberculate. Areoles of variable size. Spines variable in size and number, radiais and centrals little or no differentiation, curved, sometimes slightly hooked, “centrals” generally more robust. Young stage (non reproductive): during this phase, species are globose, smaller than the adults and do not bear the reproductive attribute which is the cephalium. The cephalium is a modified portion of the stem bearing wool and bristles densely grouped, whose function is reproduction. Reproductive stage: adult plants develop a cephalium at the apex, which becomes in some species, cylindrical and very high (up to 1 m).
Flowers diurnal, self-fertile, mostly very small, tubular, naked, immersed in the cephalium, pink, more or less carmine red, or purple, pollinated by hummingbirds (Adelomyia melanogenys, Amazilia saucerrottei, A. tzacatl, Chlorostilbon aureoventris, C. canivetti caribaeus, C. lucidus, C. stenura, Chrysolampis mosquitus, Phaethornis pretrei, Eupetomena macroura) and also by insects, especially ants (Formicinae, Myrmicinae, Polichodrinae and Ponerinae), bees and butterflies (on M. glaucescens and M. paucispinus, Colaco et al. 2006 and Lambert et al. 2006, in Emerson 2007). Fruits naked, elongated, often davate, juicy, containing mucilage, appearing in the cephalium, floral remains persistent, white, pink, magenta red or pinkish. Seeds rather small, often numerous (+ 400), globose to egg-shaped, striate, warty, black. Dispersal of seeds insured through myrmecochory = ants (Ectatomma edentatum, cromyrmex laticeps nigrosetosus, Solenopsis substituta, Dorymyrmex thoracicus), ornithochory = birds, and saurochory = lizards, (Cnemidophorus ocellifer, Microlophus spp., Tropidurus cocorobensis, T. torquatus).
The genus Melocactus grows from South America up to Mexico and in the Caribbean islands, usually in warm and wet or relatively dry tropical regions, on crystalline (gneiss or granite) rocky outcrops, in crevices, sandy, clayey or siliceous areas, on serpentines, altered sandy conglomerates, soils of volcanic origin, andesites, also ferruginous soils, quartz gravels, in mountainsides among rocks, on rocky hillslopes, as well in full sun as in the shade of shrubs, in light woodlands, savannas, deserts, in valleys, sometimes close to the ocean, on dunes of pure quartz sand, on beaches, receiving sea spray, from sea level (M. intortus) up to 2160 m in altitude (M. bellavistensis subsp. onychacanthus), together with other cacti and succulents, as well as caudiciform plants and bromeliads.
The Antilles (Aruba, Bonaire, Curacao, Grenada, St Vincent), Bahamas, Brazil (Alagoas, Bahia, Ceara, Espirito Santo, Minas Gerais, Paraiba, Pernambuco, Piaui, Rio de Janeiro, Rio Grande do Norte, Roraima, Sergipe), Colombia (Boyaca, Cauca, Cundinamarca, Guajira, Huila, Magdalena, Santander, Tolima, Valle, Vichada), Costa Rica (Guanacaste), Cuba (Camaguey, Guantanamo, Holguin, Matanzas, Santa Clara, Santiago of Cuba), Ecuador (Loja), French Antilles
(Guadeloupe, La Desirade, Les Saintes, Marie-Galante, Martinique, Saint Barthelemy, Saint Martin), Guatemala (Baja Verapaz, Chiquimula, El Progreso, Quiche, Zacapa), Guyana, French Guyana, Honduras (Comayagua), Haiti, Jamaica, Mexico (Chiapas, Colima, Jalisco, Michoacan, Oaxaca, Veracruz), Nicaragua, Panama (Capira), Peru (Amazonas, Ancash, Arequipa, Cajamarca, La Libertad, Lambayeque, Lima, Piura, Tumbes), Puerto Rico, Dominican Republic (Pedernales),
Surinam (Nickerie, Saramacca), Trinidad and Tobago, Venezuela (Amazonas, Anzoategui, Apure, Aragua, Bolivar, Carabobo, D.F., Falcon, Guarico, Lara, Isla Margarita, Merida, Nueva Esparta, Sucre, Tachira, Trujillo, Zulia), Virgin Islands (Antigua).

Currently 50 recognised species plus 17 subspecies and with one (or more ) supposed hybrid:
– Melocactus acunae Leon 1934
– Melocactus acunae subsp. lagunaensis Meszaros 1977
– Melocactus x albicephalus Burning & Brederoo 1973
– Melocactus alex-bragal P.J.Braun & E.Esteves 2008
– Melocactus andinus R.Gruber ex N.P.Taylor 1991
– Melocactus andinus subsp. hernandezii (Fernandez & Xhonneux) N.P.Taylor 2003
– Melocactus azureus Burning & Brederoo 1971
– Melocactus baliiensls (Britton & Rose) Luetzelberg 1923
– Melocactus bahiensis subsp. amethystinus (Burning & Brederoo) N.P.Taylor 1991
– Melocactus bellavlstensis Rauh & Backeberg 1957
– Melocactus bellavistensis subsp. onychacanthus (F.Ritter) N.P.Taylor 1991
– Melocactus borhidii Meszaros 1977
– Melocactus braunii E.Esteves 2003
– Melocactus brederooianus Burning 1972
– Melocactus broadwayl (Britton & Rose) A.Berger 1926
– Melocactus caroli-linnaei* N.P.Taylor 1991
– Melocactus concinnus Burning & Brederoo 1972
– Melocactus conoideus Burning & Brederoo 1973
– Melocactus curvispinus* Pfeiffer 1837
– Melocactus curvispinus subsp. caesius (H.Wendl.) N.P.Taylor 1991
– Melocactus curvispinus subsp. dawsonii (Bravo) N.P.Taylor 1991
– Melocactus curvispinus subsp. koolwljklanus (Suringar) Thomson 2002
– Melocactus curvispinus subsp. saravianus Fernandez Alonso & Xhonneux 2002
– Melocactus deinacanthus Burning & Brederoo 1973
– Melocactus ernestii Vaupel 1920
– Melocactus ernestii subsp. longlcarpus (Burning & Brederoo) N.P.Taylor 1991
– Melocactus estevesii P.J.Braun 1989
– Melocactus evae Meszaros 1977
– Melocactus ferreophllus Burning & Brederoo 1973
– Melocactus glaucescens Burning & Brederoo 1972
– Melocactus guanensis Xhonneux & Fernandez 2001
– Melocactus harlowli (Britton & Rose) Vaupel 1912
– Melocactus holguinensis Areces 1976
– Melocactus inconcinnus Burning & Brederoo 1975
– Melocactus intortus* (Mill.) Urban 1919
– Melocactus intortus subsp. domingensls Areces 1997 (= M. pedernalensis)
– Melocactus krainzianus Burning & Brederoo 1975
– Melocactus lanssenslanus P.J.Braun 1986
– Melocactus lemairei (Monville ex Lemaire) Miquel ex Lemaire 1840
– Melocactus levistestatus Burning & Brederoo 1973
– Melocactus macracanthos (Salm-Dyck) Link & Otto 1827
– Melocactus matanzanus Leon 1934
– Melocactus mazelianus Riha 1981
– Melocactus nagyi Meszaros 1977
– Melocactus neryi K.Schumann 1901
– Melocactus oreas* Miquel 1840
– Melocactus oreas subsp. cremnophilus (Burning & Brederoo) P.J.Braun 1988
– Melocactus pachyacanthus Burning & Brederoo 1975
– Melocactus pachyacanthus subsp. viridis N.P.Taylor 1991
– Melocactus paucispinus Heimen & Paul 1983
– Melocactus perezassoi Areces 1993
– Melocactus peruvianus Vaupel 1913
– Melocactus pescaderensis Xhonneux & Fernandez 2002
– Melocactus praerupticola Areces 2000
– Melocactus radoczii Meszaros 1977
– Melocactus roraimensis P.J.Braun & Esteves 1991
– Melocactus salvadorensis Werdermann 1934
– Melocactus saxicola Diers & Esteves 1984
– Melocactus schatzlii H.Till & R.Gruber 1982
– Melocactus schatzlii subsp. chicamochae Fern. & Xhon. 2002 (ex M. andinus subsp. soatensis)
– Melocactus smithii (Alexander) Burning ex G.D.Rowley 1976
– Melocactus stramineus Suringar 1886
– Melocactus violaceus Pfeiffer 1835
– Melocactus violaceus subsp. margaritaceus N.P.Taylor 1991

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