≪Winged Cactus≫, referring to the characteristic winged seeds of the genus.
A genus of geophytic dwarf plants with large tuberous roots; stems segmented, globose or cylindrical, breaking and rooting easily, often papillose, often disappearing in the dry season; areoles having spines and glochids are present or absent according to species. Spines finely aciculate or subulate, curved, sometimes papery. Leaves tiny, soon deciduous.
Flowers diurnal, self-sterile, rotate emerging directly from stem tips, yellow to reddish or reddish brown, with slightly tuberculate pericarpel and bearing fine spines, pollinated by hymenoptera. Stamens sensitive to contact. Fruits dry, capsule-like with lateral dehiscence, densely covered with spines. Seeds large, pale yellow to light brown, more or less circular, typically with a papery winged membrane, lightweight, for wind-pollinated dispersal (anemophily).
The genus Pterocactus grows essentially from Patagonia into northern Argentina, in small colonies on sandy or clayey soils, sometimes salt plains, on gentle sloping hills, also on rocky soils, near the coast, practically from sea level (P. valentinii) up to 3050 m in altitude (P. megliolH). The genus was originally considered endemic to Argentina, but populations were recently discovered in southern Chile (Kiesling 2002). In some regions, Pterocactus can endure severe frosts.
Argentina (Buenos Aires, Catamarca, Chubut, Cordoba, Jujuy, Pampa, Rioja, Mendoza, Neuquen, Rio Negro, Salta, San Juan, Santa Cruz, Tucuman), Chile (Aisen).
Currently 9 recognised species:
– Pterocactus araucanus A.Castellanos 1964
– Pterocactus australis (Weber) Backeberg 1950
– Pterocactus fischeri Britton & Rose 1914
– Pterocactus gonjianii* R.Kiesling 1982
– Pterocactus hickenii Britton & Rose 1919
– Pterocactus megliolii* R.Kiesling 1971
– Pterocactus reticulatus R.Kiesling 1971
– Pterocactus tuberosus* (Pfeiffer) Britton & Rose 1919 (= P. decipiens?, = P. kuntzei?)
– Pterocactus valentina* Spegazzini 1899
References: "TAXONOMY of the CACTACEAE" - ISBN 978-84-617-3692-8 (Vol. 2)