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| The genera of Cactaceae |
~ Mammillaria, cf. Hunt (1967)
The plants condensed-cactoid; low and very compacted in their entirety. The plants’ appearance dominated by crowded interlacing areolar structures obscuring any tubercles, ribs or furrows. The stems very spiny; depressed- discoid to globose, or shortly cylindric; 6–14 cm in diameter; apically depressed, or not apically depressed. The plants erect; solitary to clustering; to 0.3 m high. The stems not segmented; not ribbed and grooved. The plants conspicuously tuberculate. The tubercles broadly cylindrical, blunt; neither grooved nor ridged adaxially. The tubercles not connected by ribs; spirally disposed. The areoles associated with tubercles; closely approximating. The components of adjacent areoles so extensively covering the mature plant body as to obscure any ribs or furrows. The areoles spirally disposed; 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 (the axils with 4–7 white bristles). The flowering areoles resembling the non-flowering ones. The areoles with spines. The spines clustered (in several series); about 70–130; 0.2–1.5 cm long; with radials and centrals differentiated (the centrals to 10 mm long and white with pinkish tips, the very numerous radials to 15 mm long, spreading, white). Central spines 8–12. Radial spines 50–120 (? - "very numerous"). The spines never hooked. The mature stems leafless.
Flowering during the day. The flowers lateral (but often forming a circle behind the apex); one per areole (at the bases of the tubercles); sessile; small to medium-sized; 2–3 cm long; regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium; naked. The hypanthial tube naked; without scales; spineless. The perianth white and red, or white, or pink. The perianth segments elongate, relatively narrow to relatively short, broad; pointed.
The mature fruit 0.7–1.4 cm long; ovoid; white (-ish), or red, or pink; fleshy; indehiscent. The seeds 1 mm long; "with flat or domed testa"; with little or no perisperm; not encased in bony arils. The testa "not pitted". Cotyledons reduced or vestigial.
Natural Distribution. Northeastern Mexico.
Classification. 1 species (M. candida). Subfamily Cactoideae. Tribe Cacteae.
Though recently retained by the International Cactaceae Systematics Group as a monotypic genus, in the 1976 edition of Backeberg’s Lexicon this ‘genus’ was dismissed as having been based on misidentified seed material.
Images. • Mammilloydia candida: © elite-pets.narod.rn.
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’.
