in Ariocarpus. The species Lophophora williamsii (peyote) was placed in Anhalonium at one time, although not in Ariocarpus. Species , Plants of the World Online accepted the following species and natural hybrids: Natural Hybrids Ariocarpus × drabi Halda & Sladk. (=A. kotschoubeyanus × A. retusus) Distribution and habitat With one exception, the genus is native to the central parts of Mexico, the northeast and the southwest. It is absent from the west, including Baja California, and from the southeast, including Yucatán. Ariocarpus fissuratus has a native range that extends from Mexico into south and southwest Texas in the United States, being found in the Chihuahuan Desert on both sides of the border. Ariocarpus is strongly adapted to harsh dry conditions. Large underground roots make up much of the plant; the stem grows close to the soil (or even below it) and has a thick upper surface (epidermis). Cultivation While very slow growing, a number of species, A. retusus for instance, are not particularly difficult to keep. Ariocarpus species have a tuberous root system and are quite sensitive to soil conditions, preferring sharply draining loam based soils with minimal humus. Care should be taken to avoid overwatering, allowing the soil to dry out completely between waterings. Plants require water only during periods of summer growth and should be kept perfectly dry overwinter, with a minimum temperature of 12 °C, although certain species can cope with considerably cooler conditions. Propagation is by seed and, although slow, is not necessarily difficult. Ariocarpus seedlings are often grafted on Pereskiopsis in order to considerably increase their growth rate, more mature plants may be regrafted onto Echinopsis, Eriocereus or Opuntia compressa for better hardiness, though such plants often bear little resemblance to ungrafted specimens. References Bibliography Innes C, Wall B (1995). Cacti Succulents and Bromaliads. Cassell & The Royal Horticultural Society. External links Ariocarpus - living rocks of Mexico Cactus-mall.com: "Lost Peyotls" Cacti of Mexico Flora of Texas Cactoideae genera