Autor: Pfeiffer
• ETYMOLOGY
“Cactus-disc”, referring to the flat-round disc-shape of some species in the genus, when they were first described.
• DESCRIPTION
A genus of low-growing plants generally solitary, globose, more or less flattened, with numerous tuberculate ribs, with areoles covered by spines. Usually, spines are robust, often flattened at the base and curved. Apical cephalium densely woolly from which appear stiff bristles.
Flowers nocturnal, sometimes self-fertile, appearing rapidly when buds emerge from the cephalium, strongly scented, funnel-shaped, white, with a slender floral tube, pollinated by Sphingideae. Fruits globose to clavate or elongated, slightly fleshy, fragile, usually white to more or less tinged with pink, with lateral dehiscence, retaining the remains of dried perianth. Seeds shiny, covered with papilla, or tuberculate, black. Dispersion essentially myrmecophilous, also
reported a case of hydrochory with Discocactus bahiensis (Taylor & Zappi 2004).
• HABITAT
The genus Discocactus usually grows at ground level, in small scattered colonies, sometimes together with other cacti, succulents, orchids and Bromeliads, in the mountains and plateaus of northern Brazil and neighbouring countries (Bolivia and Paraguay), on rocky platforms, in the shade of bushes and spiny shrubs, or in full sun (D. silicicola), on rocky, clay or sandy soils (D. hartmannii), detrital, sometimes of volcanic origin, or in sandstone crevices, ferruginous
red earths, or manganesiferous black soil, siliceous gravels or fine crystalline sand, yellow or white quartz (D. horstii), in pockets of humus, also alluvial areas or on slopes of rocky hills, in very open woodlands, from 100 m (D. ferricola) up to 1300 m in altitude (D. placentiformis). In periods of drought, some species become mimetic, often covered with soil and various organic debris which protect them from the sun and dessication. Some species such as D. silicicola, may withstand minimum temperatures of only +5°C in winter in their habitat.
• DISTRIBUTION
Bolivia (Santa Cruz), Brazil (Bahia, Ceara, Goias, Maranhao, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Pernambuco, Piaui, Tocantins), Paraguay (Amambay).
Currently 25 possible species + 14 subspecies
– Discocactus bahiensis* Britton & Rose 1922
– Discocactus bahiensis subsp. gracilis P.J.Braun & Esteves 2001
– Discocactus bahiensis subsp. subviridigriseus (Buin. & Bred.) P.J.Braun & Esteves 1993
– Discocactus boliviensis Backeb. 1963
– Discocactus cangaensis Diers & Esteves 1980
– Discocactus catingicola* Burning & Brederoo 1974
– Discocactus catingicola subsp. griseus (Buin. & Bred.) P.J.Braun & Esteves 1995
– Discocactus catingicola subsp. rapirhizus (Buin. & Bred.) P.J.Braun & Esteves 1993
– Discocactus cephaliaciculosus Burning & Brederoo 1995
– Discocactus crassispinus P.J.Braun & Esteves 1994
– Discocactus diersianus Esteves 1979
– Discocactus estevesii Diers & Esteves 1978
– Discocactus ferricola Burning & Brederoo 1975
– Discocactus hartmannii (K.Schum.) Britton & Rose 1922
– Discocactus hartmannii subsp. patulifolius (Burning & Brederoo) P.J.Braun & Esteves 1995
– Discocactus hartmannii subsp. setosiflorus P.J.Braun & Esteves 1994
– Discocactus heptacanthus (Rodr.) Britton & Rose 1922
– Discocactus heptacanthus subsp. magnimammus (Buin. & Bred.) N.P.Taylor & Zappi 1991
– Discocactus heptacanthus subsp. melanochlorus (Buin. & Bred.) P.J.Braun & Esteves 1993
– Discocactus horstii Burning & Brederoo ex Burning 1973
– Discocactus latispinus Burning & Brederoo 1976
– Discocactus latispinus subsp. pulvinicapitatus (Buin. & Bred.) P.J.Braun & Esteves 1993
– Discocactus lindanus Diers & Esteves 1981 (“lindaianus”)
– Discocactus pachythele Burning & Brederoo 1975
– Discocactus petr-halfari M.Zachar 2008
– Discocactus piauiensis P.J.Braun & Esteves 1995
– Discocactus placentiformis* (Lehm.) K.Schum. 1894
– Discocactus placentiformis subsp. multicolorispinus (P.J. Braun & Brederoo) P.J. Braun & Esteves 1993
– Discocactus placentiformis subsp. pugionacanthus (Buin. & Bred.) P.J.Braun & Esteves 1995
– Discocactus prominentigibbus Diers & Esteves 1988
– Discocactus pseudoinsignis N.P.Taylor & Zappi 1991
– Discocactus silicicola Burning & Brederoo 1975
– Discocactus silvaticus Burning & J. Theunissen 1977
– Discocactus squamibaccatus Burning & Brederoo 1977
– Discocactus subterraneo-proliferans Diers & Esteves 1980
– Discocactus zehntneri* Britton & Rose 1922
– Discocactus zehntneri subsp. albispinus (Buin. & Bred.) P.J.Braun & Esteves 1995
– Discocactus zehntneri subsp. boomianus* (Buin. & Bred.) N.P.Taylor & Zappi 1991
– Discocactus zehntneri subsp. buenekeri* (Abraham) P.J.Braun & Esteves 1993
References: "TAXONOMY of the CACTACEAE" - ISBN 978-84-617-3723-9 (Vol. 1)