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| The genera of Cactaceae |
~ Gymnocalycium, cf. Hunt (1967)
The plants condensed-cactoid; low and very compacted in their entirety. The stems spiny; discoid to globose (stoutly tap-rooted); 5–10 cm in diameter; apically depressed, or not apically depressed. The plants unbranched; erect; solitary; to 0.04–0.1 m high. The stems not segmented; indistinctly ribbed and grooved. The ribs 15–16(–18); borne spirally; deeply divided into tubercles. The grooves deep and narrow. The plants very conspicuously tuberculate. The tubercles prominent; neither grooved nor ridged adaxially. The tubercles connected by the ribs; spirally disposed. The areoles conspicuously associated with tubercles; distant; spirally disposed; simple (often sunken, towards the bases of the adaxial sides of the tubercles); with spines. The spines clustered; 1–22; 0.8–2.2 cm long; with radials and centrals differentiated (the centrals to 2 cm or more long, often hooked, the numerous radials shorter). Central spines 1–3. Radial spines 5–20. The spines stiff, or flexible; often usually including some hooked members; straight, or curved, or hooked. The mature stems leafless.
Flowering during the day. The flowers terminal (borne on the upper tubercles); one per areole to more than one per areole; funnelform; sessile; small; in N. vorwerkii, 1.8–2 cm long (and in diameter); regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium to scarcely produced beyond the ovary. The pericarpel with fleshy scales and naked areoles. The hypanthial tube ornamented like the pericarpel; not naked; with scales (these fleshy). The axils of the scales of the hypanthial tube not naked (with naked areoles). The hypanthial tube spineless. The perianth lilac- pink, or white. The perianth segments relatively short, broad; pointed.
The mature fruit to 0.5 cm long; globose; non-fleshy when mature; dehiscent; dehiscing vertically by one slit, or dehiscing vertically by more than one slit ("laterally"). The seeds broadly oval, ruminate; not encased in bony arils; with hilum and micropyle conjunct. Cotyledons reduced or vestigial.
Natural Distribution. Northern Argentina, southern Bolivia, Peru, northern Chile.
Classification. 2 species. Subfamily Cactoideae. Tribe Notocacteae.
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’.