|
| The genera of Cactaceae |
~ Opuntia, cf. Hunt (1967)
Including Pseudotephrocactus Fric
The plants opuntioid; not ‘low and very compacted’. The stems spiny. The plants characteristically branched (‘terminally or subterminally, so that the shoots stand in vertical rows’); without cladodes; erect; small, shrubby; to 0.1–0.3 m high. The branches (segments) cylindrical, or clavate, or globose; to 2.5–10 cm long. The stems segmented; not ribbed and grooved. The plants conspicuously tuberculate, or conspicuously tuberculate to not conspicuously tuberculate (sharply delimited or not). The tubercles not connected by ribs; spirally disposed. The areoles at least fairly convincingly associated with tubercles; distant; spirally disposed; simple (numerous per segment, sunken into globose or pyriform cavities with small openings). The flowering areoles resembling the non-flowering ones. The areoles hairy; with glochids; with spines (usually), or without spines. The spines when present, solitary to clustered; 1–15; 0.5–15 cm long; showing little or no difference between radials and centrals; without sheaths. The mature stems !.
Flowering during the day. The flowers terminal; one per areole; sessile; medium-sized to large; 3–4.5 cm long; regular. The receptacle scarcely produced beyond the ovary to not produced beyond the ovary (?); not naked; with scales (?!); spineless. The pericarpel with spineless areoles. The perianth white, or yellow, or red, or pink. The perianth segments relatively short, broad. Gynoecium inferior. The ovules circinotropus, campylotropous. The funicles circinate.
The mature fruit naked (?), or not naked; spiny, or with glochids, or spiny and with glochids, or without spines (sometimes bristly); non-fleshy when mature; dehiscent. The seeds 2.5–9.5 mm long; variable in size, with glabrous funicular envelopes and stongly protruding funicular girdles comprising thin walled cells, yellowish white to brown; not hairy; wingless; encased in their bony arils. Cotyledons fleshy, foliaceous.
Physiology. CAM.
Natural Distribution. Argentina.
Classification. 6 species. Subfamily Opuntioideae. Tribe Tephrocacteae.
Images. • Tephrocactus alexanderi: © Zoya Akulova (2007). • Tephrocactus geometricus: © Zoya Akulova (2007).
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’.
