| | The genera of Cactaceae |
Hedgehog cactus.
Including Navajoa Croizat, Pilocanthus B.W. Benson & Backeb., Utahia Br. & R.
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, or dominated neither by crowded areolar structures nor by tubercles covering the areoles. The stems spiny; diverse in appearance, depressed- globose, or discoid, or shortly cylindric; (1–)2–7(–9.5) cm in diameter; apically depressed, or not apically depressed. The plants terrestrial and self supporting, or geophytic (occasionally); mostly unbranched, or offsetting; erect; mostly solitary, or clustering; to 0.007–0.15 m high. The stems not segmented; not ribbed and grooved. The ribs borne spirally. The plants conspicuously tuberculate. The tubercles short, terete, conical or triquetrous, somewhat pyramidal, not grooved. The tubercles not connected by ribs; spirally disposed. The areoles associated with tubercles; closely approximating to distant. The components of adjacent areoles so extensively covering the mature plant body as to obscure any ribs or furrows, or not obscuring details of the plant body. The areoles spirally disposed; simple; without glochids; with spines, or with spines and without spines (these sometimes absent from the lower ones). The spines clustered; 3–45; 0.1–3.2 cm long; with radials and centrals differentiated (the 5–32 mm long, spreading, the radials 1–21 mm long, sometimes pectinate). Central spines 0, or 1–10; conspicuously forming a cross, or not forming a cross. Radial spines 3–35. The spines acicular, subular, bristly or papery, stiff, or flexible; variously straight, or curved; flattened, or terete. The mature stems leafless.
The flowers terminal (arising at the upper edges of the areoles towards the stem apex); one per areole; shortly funnelform, or campanulate; sessile; small to medium-sized; 1.2–3.5 cm long; regular. The receptacle scarcely produced beyond the ovary; not naked; with scales; spineless. The hypanthial tube not naked; with scales (these few to many, sometimes fimbriate). The axils of the scales of the hypanthial tube more or less naked. The hypanthial tube spineless. The perianth petaline, or of ‘tepals’; white, or yellow, or red, or purple. Stamens numerous, inserted in the tube; not exserted.
The mature fruit 0.3–1.2 cm long; sub- globose, or ellipsoidal, or clavate; green (-ish), or brown to red; not naked (with a few scales towards the apex); without spines; with persistent floral remains (the perianth only partly deciduous, leaving a lid-like cap); non-fleshy when mature; dehiscent; dehiscing via a circumcissile cap and a dorsal slit. The seeds blackish- brown; globose or sub-globose, or pyriform; not encased in bony arils. The testa papillate, or rugose. Cotyledons reduced or vestigial.
Natural Distribution. Western United States on the Colorado Plateau, extending into the Columbia River Basin, Great Plains and Rocky Mountains.
Classification. 8 species. Subfamily Cactoideae. Tribe Cacteae.
Cf. Hunt (1967).
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’.
