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| The genera of Cactaceae |
Living rock.
Including Anhalonium Lem., Neogomesia Castañeda, Neogomezia Buxb. (orth. var.), Roseocactus A. Berger, Stromatocactus Karw. ex Rümpler (nom. inval.)
The plants small, tap-rooted, more or less condensed-cactoid; low and very compacted in their entirety. The plants’ appearance dominated by large, crowded, semi-spherical, naked tubercles with areoles sunken between these. The plants vegetatively reduced almost entirely to rosettes of large, trigonous tubercles. The stems not spiny; in outline more or less depressed discoid. The plants epiphytic; unbranched; solitary, or clustering (i.e., sometimes clump forming). The stems not segmented; not ribbed and grooved. The plants very conspicuously tuberculate. The tubercles large, triangular, sometimes leaflike; neither grooved nor ridged adaxially. The tubercles not connected by ribs; rosetted, spirally disposed. The areoles associated with tubercles; spirally disposed. The morphologically geminate, super-imposed buds separated, with the lower one in the axil of the conspicuous tubercle that bears the upper one at its tip. The areoles simple, or distinctly bipartite, with the abaxial spine cluster at the tubercle tip and no recessed isthmus or other visible connection with the adaxial, floriferous meristem near its base (comprising woolly grooves on the upper surfaces of the tubercles, or round pads near their tips, and absent from some of them); at least when mature, usually without spines, or with spines (occasionally, in A. agavoides). The spines when present, small. The mature stems leafless.
Flowering during the day (lasting more than one day). The flowers solitary; terminal (borne at the woolly bases of young tubercles); one per areole; funnelform; sessile; medium-sized; 1.5–5 cm long (and in diameter); regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium, or scarcely produced beyond the ovary (?); naked. The perianth white, or yellow, or pink, or purple. The perianth segments spreading; relatively short, broad; blunt, or apiculate. Stamens numerous; adnate to the perianth (inserted in the tube and throat); not exserted. The stigma lobes white.
The mature fruit 0.8–2.5 cm long; sub- globose, or clavate; where recorded, brown (or pinkish or purplish when immature); naked; fleshy to non-fleshy when mature (fleshy at first); indehiscent (disintegrating). The seeds black; pyriform; not encased in bony arils. The testa tuberculate. Cotyledons reduced or vestigial.
Natural Distribution. Northern Mexico, western Texas.
Classification. 6 species. Subfamily Cactoideae. Tribe Cacteae.
Cf. Hunt, 1967.
Images. • Ariocarpus retusus: © Zoya Akulova (2014). • Ariocarpus kotschonbeyanus, with Pediocactus simpsonii, Denmoza rhodacantha and Eriosyce subgibbosa (as Neoporteria): Britton & Rose (1922). • Ariocarpus retusus, with Lophophora williamsii: Britton & Rose (1922).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2018 onwards. The genera of Cactaceae: descriptions, illustrations, identification, and information retrieval. Version: 14th November 2021. delta-intkey.com’.
