| | The genera of Cactaceae |
The plants succulent; condensed-cactoid; low and very compacted in their entirety. The plants’ appearance dominated neither by crowded areolar structures nor by tubercles covering the areoles. The stems spiny; globose, or shortly cylindric; apically depressed, or not apically depressed; neither cephaliate nor pseudocephaliate. The plants to 0.015–0.06 m high. The stems not segmented; shallowly ribbed and grooved. The ribs 8–31; longitudinal. The plants usually, more or less conspicuously tuberculate to not conspicuously tuberculate. The tubercles neither grooved nor ridged adaxially. The tubercles connected by the ribs; borne in longitudinal series. The areoles associated with tubercles (but ribs and tubercles weak); closely approximating to distant; borne in longitudinal series; simple; without glochids; with spines. The spines clustered; 3–18(–26); 0.1–0.6 cm long; with radials and centrals differentiated to showing little or no difference between radials and centrals. Central spines when differentiated, (0–)1–6. Radial spines when differentiated, 9–20. The spines weak, stiff, or flexible; never hooked. The mature stems leafless.
Flowering during the day. The flowers terminal; one per areole; shortly funnelform, or campanulate (or sometimes cleistogamous); sessile; small to medium-sized; 2–4 cm long; regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium to scarcely produced beyond the ovary. The hypanthial tube short; not naked; with scales (these small). The axils of the scales of the hypanthial tube not naked (with woolly hairs and bristles). The hypanthial tube spineless. The perianth yellow. The perianth segments relatively short, broad; blunt to pointed, or apiculate. Stamens not exserted; not grouped.
The mature fruit 0.4–2 cm long; not naked (scaly); without spines; with persistent floral remains; small, thin walled, non-fleshy when mature; dehiscent to indehiscent; if dehiscent, irregularly dehiscent. The seeds 1.5 mm long; brown to black; ovoid to obliquely ovoid, or helmet- or hat-shaped, or cochleate (hemispherical or hat-shaped, and 1.5 cm in diameter, sometimes somewhat beaked); not encased in bony arils. The testa shiny; spiculate, or spiculate and verrucose (somewhat verrucose and sometimes minutely spiculate), or smooth, without ornamentation (apart from a network of darker lines). Cotyledons reduced or vestigial.
Natural Distribution. Northeastern Argentina, eastern Bolivia, Columbia, southern Brazil, Paraguay, Uraguay. Central America.
Classification. 18 species. Subfamily Cactoideae. Tribe Notocacteae.
Cf. Hunt, 1967.
Images. • Frailea pumila: 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’.
