| | The genera of Cactaceae |
Chin cactus.
Including Brachycalycium Backeb.
The plants condensed-cactoid; low and very compacted in their entirety. The stems spiny; discoid, or globose, or shortly cylindric; apically depressed; neither cephaliate nor pseudocephaliate. The plants unbranched (usually), or offsetting; erect; solitary (usually), or clustering; to 0.01–0.2 m high. The stems not segmented; strongly ribbed and grooved. The ribs 4–15(–20); borne spirally, or longitudinal; usually broadly rounded, notched into warts or tubercles, with a more or less pronounced protuberance or ‘chin’ beneath each areole. The grooves wide to deep and narrow. The plants variously conspicuously tuberculate to not conspicuously tuberculate. The tubercles variable. The tubercles when present, connected by the ribs; spirally disposed, or borne in longitudinal series. The areoles associated with tubercles, or not tubercle-associated; distant; large, spirally disposed, or borne in longitudinal series; simple. The flowering areoles resembling the non-flowering ones. The areoles slightly woolly to not woolly; with spines. The spines clustered; (1–)5–10(–18); 0.6–3(–6) cm long; with radials and centrals differentiated, or showing little or no difference between radials and centrals (centrals often absent). Central spines when present and differentiated, 1–3(–7). Radial spines (3–)5–15. The spines never hooked; variously straight, or curved, or straight and curved; flattened, or flattened and terete. The mature stems leafless.
Flowering during the day. The flowers terminal (borne at or near the stem tips); one per areole; glabrous funnelform to campanulate; sessile; mostly large; (1–)3–8(–11) cm long; regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium to scarcely produced beyond the ovary; not naked; with scales; spineless. The pericarpel bearing a few broad, obtuse scales with characteristically hyaline margins and naked axils. The hypanthial tube not naked; with scales (a few, broad, obtuse with hyaline margins). The axils of the scales of the hypanthial tube more or less naked. The hypanthial tube spineless. The perianth sequentially intergrading from sepals to petals, or petaline, or of ‘tepals’ (?); white, or pink, or red, or yellow (rarely). The perianth segments sub- more or less erect, or spreading; relatively short, broad; blunt, or pointed, or apiculate. Stamens very numerous; adnate to the perianth (inserted in the tube, or around the style base when the tube is much reduced); not separated from the perianth by a ring of hairs; not exserted; in groups (in two groups, the lower surrounding the style immediately above the nectar chamber, the upper inserted nearer the mouth of the tube).
The mature fruit (0.5–)1–4.2 cm long; globose, or ellipsoidal (or "obovate"); usually red; not naked (naked below but surounded by copious wool, apically densely woolly and with scales); without spines; with persistent floral remains; fleshy, or non-fleshy when mature; dehiscent, or indehiscent (variously splitting, cracking or deliquescent when ripe); if dehiscent, variously dehiscing vertically by one slit, or dehiscing vertically by more than one slit, or irregularly dehiscent. The seeds brown, or black; globose or sub-globose, or ovoid (or lenticular); not encased in bony arils; with a strophiole obscuring the hilum (often), or without a strophiole hiding the hilum. The testa minutely spiculate, or verrucose, or smooth, without ornamentation. Cotyledons reduced or vestigial.
Natural Distribution. Brazil, Paraguay, Bolivia, Uruguay, Chile, Argentina.
Classification. About 60 species. Subfamily Cactoideae. Tribe Trichocereeae.
Cf. Hunt (1967).
Images. • Gymnocalycium andreae: © Zoya Akulova (2007). • Gymnocalycium andreae: © Zoya Akulova (2007). • Gymnocalycium monvillei: © Zoya Akulova (2007). • Gymnocalycium monvillei: © Zoya Akulova (2007). • Gymnocalycium spegazzinii: © Zoya Akulova (2007). • Gymnocalycium mostii and G. saglionis: Britton & Rose (1922). • Gymnocalycium megalothelon, G. monvillei (as multiflorum), G. platense: Britton & Rose (1922). • Gymnocalycium platense and G. schickendantzii, with Echinocactus texensis (as Homalocephala): Briton & 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’.
