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| The genera of Cactaceae |
Including Aylostera Speg., Bridgesia Backeb., Cylindrorebutia Fric & Kreuz., Digitorebutia Fric & Kreuz., Echinorebutia Fric (nom. inval.), Eurebutia Fric (nom. inval.), Gymnantha Y. Itô, Mediolobivia Backeb., Mediorebutia Fric (nom. inval.), Neogymnantha Y. Itô, Reicheocactus Backeb., Setirebutia Fric & Kreuz. (nom. inval.), Spegazzinia Backeb., Sulcorebutia Backeb., Weingartia Werderm.
The plants succulent; cerioid (rarely, e.g. some Mediolobivia spp.), or condensed-cactoid (usually, sometimes tap-rooted); low and very compacted in their entirety, or not ‘low and very compacted’ (rarely); not vegetatively reduced to tubercles. The stems spiny; globose, or shortly cylindric; apically depressed to not apically depressed; neither cephaliate nor pseudocephaliate. The plants usually basally freely branched (from the base), or offsetting; without cladodes; erect; solitary, or clustering; to 0.01–0.3 m high. The main stem globose, or more or less cylindrical. The branches cylindrical, or globose. The stems not segmented; not ribbed and grooved, or ribbed and grooved to not ribbed and grooved (i.e., the ribs poorly developed, or absent). The ribs if present, longitudinal. The plants at least usually conspicuously tuberculate. The tubercles connected by the ribs to not connected by ribs (then replacing them, e.g. Mediolobivia spp.); spirally disposed. The areoles more or less associated with tubercles, or not tubercle-associated. The morphologically geminate, super-imposed buds very close, forming single areoles. The areoles simple (round or elliptic to linear). The flowering areoles resembling the non-flowering ones. The areoles not woolly; without glochids; with spines (but usually "bristly"). The spines or bristles clustered; (3–)7–20(–40); 0.05–2(–5) cm long; with radials and centrals differentiated to showing little or no difference between radials and centrals; weak, usually bristly. The mature stems leafless.
Flowering during the day. The flowers solitary, or aggregated; lateral; one per areole (but often numerous); funnelform (with a slender tube); sessile (but appearing stalked in Aylostera); usually fairly small to medium-sized; 1.5–5 cm long; regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium to scarcely produced beyond the ovary. The pericarpel slender, often curved, naked or sometimes with numerous small scales naked or hairy in their axils, the lower part solid in Aylostera. The hypanthial tube cf. the pericarpel; naked, or not naked; with scales, or without scales. The axils of the scales of the hypanthial tube more or less naked, or not naked. The hypanthial tube spineless. The perianth yellow to orange (mostly), or red, or purple. The perianth segments relatively short, broad; blunt, or pointed, or apiculate. Stamens adnate to the perianth (inserted in the throat and tube); not grouped (in a single series).
The mature fruit 3–7 cm long (or rather, 3–7 mm in diameter in the pitifully small sample recorded); sub- globose; naked, or not naked (then with small scales); without spines; with persistent floral remains, or without persistent floral remains; small, thin walled, non-fleshy when mature; indehiscent. The seeds minute; with truncate basal, often strophiolate hilum, black; semi-elliptic; not encased in bony arils; with a strophiole obscuring the hilum, or without a strophiole hiding the hilum; without a mucilage sheath. The testa shiny; verrucose to rugose, or papillate, verrucose, and rugose (i.e., verrucose or wrinkled, often distally papillate). Cotyledons reduced or vestigial.
Natural Distribution. Eastern Andes and adjacent hills of Bolivia and northwestern Argentina.
Classification. About 40 species. Subfamily Cactoideae. Tribe Trichocereeae.
Cf. Hunt (1967).
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’.
