A REVISION OF ARIOCARPUS (CACTACEAE). III. FORMAL TAXONOMY OF THE SUBGENUS ROSEOCACTUS

This is the second of 2 articles (Nos. III and IV) dealing with the formal taxonomy of Ariocarpus. A description of the genus and a key to the subgenera and species appeared in the third article of the series. This article includes a description, illustrations, a map of authenticated collection sites, citation of common names, a discussion of synonymy and types, and a list of specimens examined of each species in the subgenus Ariocarpus. The accepted species which are discussed are Ariocarpus retusus, A. agavoides, A. trigonus, and A. scapharostrus. THE FIRST 2 articles of this series (Anderson, 1960, 1962) delimited the characters of Ariocarpus and showed that 2 previously segregated genera, Roseocactus and Neogornesia, have numerous characters in common with Ariocarpus and should be included within the genus. The third article (Anderson, 1963) colntained an introduction to the formal taxonomy of the genus with sections on geographical distribution and habitat, policy of classification, herbaria consulted, and acknowledgments. A description of the genus and a key to the subgenera and species was followed by a formal taxonomic treatment of the subgenus Roseocactus. This final article dealing with the formal taxonomy of Ariocarpus treats the species of the subgenus Ariocarpus. The treatment of each species includes a description, illustrations, a map of authenticated collection sites, citation of common names, a discussion of synonymy and types, and a list of specimens examined. 3. ARIOCARPUS RETUSUS Scheidweiler Ariocarpus retusus Scheidweiler, Bull. Acad. Sci. Brux. 5: 492. 1838. Anhalonium prismaticumn Lemaire, Cact. Gen. Nov. Sp. 1. 1839. Anhaloniumn retusumn Salm-Dyck, Cact. Hort. Dyck 5, 77. 1850. Anhaloniurn elongatumn Salm-Dyck, Cact. Hort. Dyck 5, 77. 1850. M31amnmillaria aloides Monv. Cat. ex. Labour. Monog. Cact. 153. 1853, nom. nud. Anhaloniumn areolosumn Lemaire, Illus. Hort. 6, Misc. 35. 1859. Anhaloniurn pulvilligerurn Lemaire, Illus. Hort. 16: 72. 1869. I Received for publication June 11, 1963. 2 This study was made possible by the late Dr. Gordon A. Alles of Pasadena, California, who made a grant to Pomona College, Claremont, California, for the research. The writer also wishes to thank Dr. Lyman Benson of Pomona College for his advice and criticism. M11a,nnillaria aloides pulvilligera MIonv. ex. Lemaire, Illus. Hort. 16: 72. 1869. Jllammnillaria areolosa Hemsley, Biol. Celntr. Amer. Bot. 1: 503. 1880. Mamminillaria elongata Hemsley, Biol. Centr. Amer. Bot. 1: 509. 1880. Mliamimitlaria prismatica Hemsley, Biol. Centr. Amer. Bot. 1: 519. 1880. Mammnillaria furfuracea Watson, Proc. Amer. Acad. 25: 150. 1890. Cactus prismaticus Kuntze, Rev. Gen. PlI. 1: 261. 1891. Anhaloniumn furfuraceumn Coulter, Colntr. U. S. Nat. Herb. 3: 130. 1894. Ariocarpus furfuraceus Thompson, Rept. Mo. Bot. Gard. 9: 130. 1898. Ariocarpus pulvilligeris K. Schumann in Engler, Bot. Jahrb. 24: 550. 1898. Ariocarpus prisinaticus Cobbold, Jour. Hort. Cot. Gard. Home Farm. III, 46: 332. 1903. Ariocarpus furfuraceus var. rostratus Berger, Kakteen 334. 1929. Ariocarpus elongatus Wettsteini, Kakteenkunde 1933: 13. Plant grayor blue-greeni, rising slightly above ground level, globose, rounded on top, 3-12 cm high, 10-25 cm in diam.; tubercles divergent, erect, crowded and basally compressed, usually becoming attenuate at the apices, convex or nearly flattened adaxially and often with shallow adaxial unidulations or wrinkling, not fissured, 1.5-4 cm long, 1-3.5 cm broad, nearly as broad as long; spine-bearing portions of the areoles at the tips of the tubercles, rounded, 1-5 mm in diam.; flowers 4-5 cm in diam., 2-4.2 cm long; outer perianth parts white, occasionally with reddish midribs, 1.2-2 cm long, 5-8 mm broad; inner perianth parts white or rarely magenta, 1.4-2 cm long, 5-9 mm broad; pistil not exserted above the stamens; style 1.4-2.1 cm long; stigmas 7-16, 2.5-9 mm long; fruit white, green, or rarely pinkish, 10-25 mm long, 3-10 mm in diam. A species having great variation in size and shape of tubercles (Fig. 1, 2).