One of the most interesting of the cushion- or mat-forming cacti occurs in the southern Andes and the Patagonian region of South America. It forms dense cushions and grows in areas subjected to frequent frosts. The first plant of what would become known as Maihuenia was referred to as Opuntia caespitosa by Eduard Poeppig in 1835, but that name cannot be used for this South American plant because it had been used in 1830 by Constantine Rafinesque for what is now called O. humifusa, a North American cactus. The first valid name for these strange South American cacti is O. poep-pigii, described by Ludwig Pfeiffer in 1837. A few years later Rudolph Philippi described a second species as O. patagónica, which was collected in the interior of Patagonia in 1863. Philippi realized that the two species differed significantly from Opuntia and described the genus Maihuenia (type, O. poeppigii — M. poeppigii) in 1881, the name based on the vernacular name of the cactus, maihuén.
Maihuenia produces persistent leaves that are round in cross section, suggesting a relationship to either Pereskia or the opuntioids. Unfortunately, the remoteness of Maihuenia prevented botanists from studying the plants in the field or obtaining material for laboratory study. This shortage of information no longer exists, for Beat Leuenberger (1997) has published a thorough monograph of the genus. Moreover, Robert Wallace (pers. comm.) has also conducted extensive DNA sequencing of the group, clarifying the taxonomic position of Maihuenia and showing that Maihuenia is a distinct evolutionary line. It is now placed in its own subfamily, Maihuenioideae. The two species flower November-January, the flowers opening about midday and remaining open into late afternoon.
Maihuenia (Philippi exF. A. C. Weber) K. Schumann 1898 Pereskia subg. Maihuenia Philippi ex F. A. C. Weber 1898
Subfamily Maihuenioideae. Plants caespitose, low growing as mats or cushions to several meters wide. Stems segmented or un-segmented, succulent, globose to short cylindrical, olive green, becoming brownish with age, sometimes bearing spur shoots. Leaves small, round in cross section, persistent, conical to linear. Areoles numerous, small, bearing silky hairs. Spines usually 3, white to brown, with darker tips. Central spine one, sometimes absent, strongerthan the laterals, straight or slightly curved, sometimes flattened. Lateral spines 2, rarely absent, sometimes inconspicuous, pointing outward to lyingagainst the surface, straight to slightly curved, sometimes flexible. Flowers borne terminally on main branches or spur shoots, solitary, with spreading perianth parts, white oryellow. Fruits subglobose, oblong, or club shaped, with numerous fleshy bracts. Seeds almost circular, shiny black, smooth to slightly tuberculate. Distribution: southern South America, mostly in Patagonia.
Maihuenia patagónica (Philippi) Britton &Rose 1919
CHUPA SANGRE, SIEMPRE VERDE, YERBA DEL GUANACO Opuntia patagónica Philippi 1863 Maihuenia brachydelphys K. Schumann 1898 Maihuenia tehuelches Spegazzini 1902 Maihuenia valentinii Spegazzini 1902 Maihuenia andicola H. F. Comber 1928 Maihuenia albolanata F. Ritter 1980 Maihuenia cumulata F. Ritter 1980 Maihuenia latispina F. Ritter 1980
Plants forming cushions to 40 cm (16 in) high and 3 m (9.8 ft) wide. Taproots to 40 cm (16 in) long. Stems lax, not segmented, elongated, to 40 cm (16 in) long, 1-2 cm (0.4-0.8 in) in diameter, with numerous knoblike to cylindrical spur shoots. Leaves numerous, conical, ovoid to linear, round or elliptical in cross section, green, 2-6 mm (to 0.2 in) long, 1.5-3 mm in diameter, with acute tips. Central spine one, rigid, 3-7.5 cm (1.2-3 in) long. Lateral spines 2, rarely one or absent, sometimes inconspicuous, 0.2-0.8 cm (to 0.3 in) long, sometimes flattened against the surface. Flowers usually borne terminally on spur shoots, white. Fruits oblong to subglobose to club shaped, 2-4 cm (0.8-1.6 in) long. Distribution: southern part of the high Andes and throughout most of Patagonia, from sea level to 2400 m (7900 ft).
Maihuenia poeppigii (Otto ex Pfeiffer) Philippi ex K. Schumann 1898
CHUPA SANGRE, ESPINA BLANCA, ESPINA DEL HUANACO, HIERBA DEL GUANACO, MAIHUÉN Opuntia poeppigii Otto ex Pfeiffer 1837
Opuntia caespitosa Poeppig 1835, illegitimate name, not Rafinesque 1830 (see 0. humifusa)
Opuntia maihuen Gay 1847
Pereskia philippi F. A. C. Weber 1898, Maihuenia philippi( F. A. C. Weber) K. Schumann 1898
Plants forming mats or low cushions to 10 cm (3.9 in) high and 2 m (6.6 ft) wide. Taproots fleshy, 40-80 cm (16-31 in) long. Stems segmented, club shaped, branching from near tips, 2-6 cm (0.8-2.4 in) long, 0.8-2 cm (0.3-0.8 in) in diameter, without knoblike spur shoots. Leaves numerous, linear, straight to slightly curved, green, 2-10 mm (to 0.4 in) long, 1-2 mm in diameter, with acute tips. Central spine one, round to flattened above, rigid, 1-2.5 cm (0.4-1 in) long. Lateral spines 2, rarely one or absent, often inconspicuous, often flattened against the surface, to 0.6 cm (0.2 in) long. Flowers borne terminally, yellow. Fruits obovate to club shaped, 5-6 cm (2-2.4 in) long. Distribution: Chile and western Argentina from sea level to 2200 m (7200 ft).
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