| | The genera of Cactaceae |
The plants succulent; condensed-cactoid; low and very compacted in their entirety. The stems spiny; discoid to globose; 2.5–9 cm in diameter; apically depressed to not apically depressed; neither cephaliate nor pseudocephaliate. The plants geophytic; unbranched, or offsetting; erect; solitary (mostly), or clustering; to 0.02–0.12 m high. The stems not segmented; not ribbed and grooved. The plants conspicuously tuberculate. The tubercles imbricate, somewhat horny, flattened above and keeled below; longitudinally grooved adaxially from the areole towards their ‘axils’. The tubercular groove short, extending less than halfway to the ‘axil’. The tubercles not connected by ribs; spirally disposed. The areoles associated with tubercles; distant; spirally disposed; with the abaxial spine cluster at the tubercle tip connected to the adaxial floriferous meristem nearer its axil by a recessed linear isthmus or a ridge; without glochids; with spines ("bristle-like"). The spines solitary to clustered (ephemeral); 1–4; showing little or no difference between radials and centrals; mostly erect, straight, or curved (?); greyish basally, dark tipped. The mature stems leafless.
The flowers terminal; one per areole; funnelform; sessile; medium-sized; 2–3.2 cm in diameter; regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium. The pericarpel with small scales grading into sepal-like perianth parts. The hypanthial tube naked, or naked to not naked; spineless. The perianth cream, or red to violet. The perianth segments elongate, relatively narrow to relatively short, broad; pointed. Stamens not exserted.
The mature fruit elongate; not naked (scaly); without spines; with persistent floral remains; fleshy to non-fleshy when mature; dehiscent. The seeds 0.3–0.7 mm long (0.2–0.4 mm in diameter); brown; somewhat pyriform; keeled (this large, white); not encased in bony arils. Cotyledons reduced or vestigial.
Natural Distribution. Mexico, at high elevations.
Classification. 1 species (S. disciformis). Subfamily Cactoideae. Tribe Cacteae.
Cf. Hunt (1967).
Images. • Strombocactus disciformis: Britton & Rose (1923).
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’.
