Pereskia

In his excellent monograph of the genus, Beat Leuenberger (1986) describes virtually all aspects of Pereskia, remarkable cacti that to most people do not look like cacti. Bearing somewhat fleshy, flattened, long-lasting leaves and lacking large, fleshy stems, Pereskia is an oddity in the family Cacta-ceae.

Probably the first collections of Pereskia were made by Charles Plumier in the West Indies in the late seventeenth century, but none of this material has been preserved (Leuenberger 1986). Plumier described Pereskia in 1703,givinga brief description of the flower and fruit. The name honors the French scholar Nicolas-Claude Fabri de Peiresc. Carl Linnaeus rejected the name Pereskia in Species Plantarum, placing the two species that Plumier had described in the genus Cactus, as C. pereskia and C. portulacifolius. Philip Miller resurrected Plumier's name for the genus in 1754. Leuenberger designated as lectotype the Linnaean specimen labeled Cactus pereskia (= P. aculeata); "Pereskia pereskia" is not a permissible name botanically.

The 17 species of Pereskia are trees or shrubs and grow in the tropics, flowering during the rainy season. The genus has been thought to display many primitive characteristics of the family, perhaps best representing what the first cacti may have looked like (Mauseth and Landrum 1997). Careful ex amination of Pereskia reveals the distinctive spine-bearing areoles and floral cup of cacti as well as other less obvious features, particularly those of the flower.

Pereskia p. Miller 1754 Rhodocactus (A. Berger) F. M. Knuth 1935

Subfamily Pereskioideae. Plants leafy and spiny, treelike, shrubby, and often scrambling. Stems straight or zigzag, slightly fleshy. Roots sometimes thickened and tuberous. Ribs and tubercles absent. Leaves alternate, broad, flattened, deciduous, usually with petioles, somewhat fleshy, with entire margins. Areoles In the axils of the leaves, usually with wool ortrichomes, bearingspines and sometimes leaves; glochids absent. Spines solitary to numerous, unequal in length, straightornearlyso. Flowers borne terminally oraxillary, solitary orin inflorescences, rotate to bell shaped, open during the day; pericarpels or floral receptacles usually areolate, with wool, spines, hairs, or leaflike bracts. Fruits solitary orclustered, variable in shape, fleshy to juicy, indehiscent, with the wall formed mostly from the receptacle; perianth parts persistent. Seeds large, black, obovate to kidney shaped, with smooth glossy testa, 1.8-7.5 mm (to 0.3 in) long, with the micropylar end round to noselike. Distribution: lowland Neotrop-ics from southern Mexico and the Caribbean to northern Argentina and Uruguay.

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