|
| The genera of Cactaceae |
Including Astrophyton Lawr. (orth. var.), Maierocactus E.C.Rost
The plants condensed-cactoid; low and very compacted in their entirety. The stems spiny, or not spiny; discoid (or flattened), or globose; neither cephaliate nor pseudocephaliate. The plants basally branched, or unbranched, or offsetting; erect; usually solitary; to 0.02–1 m high. The stems not segmented; 4–10 ribbed and grooved (and furrowed). The ribs and furrows longitudinal. The plants not conspicuously tuberculate (the 4–8 ribs prominent or broad, flat, more or less floccose). The areoles not tubercle-associated; borne in longitudinal series (along the ribs); close-set on the ribs, simple; woolly; without glochids; variable, with spines, or without spines. The spines 6–11; 3–7 cm long; with radials and centrals differentiated, or showing little or no difference between radials and centrals. Central spines when detectable, in A. ornatum, 1. Radial spines in A. ornatum, 5–10. The spines stiff, or flexible; flattened, or terete (acicular or papery). The mature stems leafless.
Flowering during the day. The flowers terminal (from nascent areoles); one per areole; shortly funnelform (with spreading petals), or salver-shaped, the perianth limb broad, or campanulate; sessile; medium-sized to large; 6–8 cm long; regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium. The hypanthial tube not naked; with scales (these narrow, pointed, imbricate, scarious). The axils of the scales of the hypanthial tube not naked (finely long-woolly). The hypanthial tube spineless. The perianth petaline, or of ‘tepals’; yellow, or yellow and red (then reddish in the throat). The perianth segments spreading; fairly relatively short, broad; blunt. Stamens numerous, inserted in the tube; not exserted; not grouped.
The mature fruit globose; not naked (with dry scales and dense hair); without spines; with persistent floral remains; slightly fleshy; irregularly dehiscent to indehiscent. The seeds to 2.5 mm long; brown to black; somewhat cap-shaped with an inrolled edge around the hilum; not encased in bony arils. The testa shiny; more or less smooth, without ornamentation. Cotyledons reduced or vestigial.
Natural Distribution. North America and Central America.
Classification. 4–6 species. Subfamily Cactoideae. Tribe Cacteae.
Cf. Hunt, 1967.
Images. • Astrophytum asterias: © Zoya Akulova (2014). • Astrophytum asterias: © Zoya Akulova (2015). • Astrophytum capricorne: © Zoya Akulova (2016). • Astrophytum capricorne, with Parodia sellowii (as Malacocarpus tephracanthus): Britton & Rose (1922). • Astrophytum myriostigma, with Parodia mammulosa (as Malacocarpus), Mila caespitosa and Eriosyce islayensis (as Malacocarpus): 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’.
