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| The genera of Cactaceae |
Old man cactus.
Including Haseltonia Backeb., Neodawsonia Backeb., Pilocereus Lem.
The plants cerioid; not ‘low and very compacted’. The stems densely spiny (often so as to obscure the stem tips); elongate cylindric; cephaliate to pseudocephaliate. The plants branched, or unbranched; erect; shrubby, or tree-like; to 10–12 m high. The stems columnar. The main stem more or less cylindrical (to 40 cm in diameter). The branches cylindrical (light green, greying with age). The stems segmented, or not segmented; ribbed and grooved. The ribs 20–30 (or more); longitudinal. The plants not conspicuously tuberculate. The areoles not tubercle-associated; closely approximating, or confluent (in the cephalia). The confluent areoles terminating the stems, or lateral. The components of adjacent areoles so extensively covering the mature plant body as to obscure any ribs or furrows to not obscuring details of the plant body. The areoles borne in longitudinal series (along the ribs); more or less simple (when not confluent). The flowering areoles differing in form from the non-flowering ones (the flowering ones in the cephalia without spines). The areoles with spines (the sterile ones), or without spines. The spines of the non-flowering areoles clustered; 10–35; 0.5–12 cm long; with radials and centrals differentiated (the centrals yellowish to grey, to 8 cm long, the more numerous, bristle- or hairlike radials longer or shorter, white, usually densely covering the stem). Central spines 1–6. Radial spines 9–20(–30). The mature stems leafless.
Flowering at night. The flowers terminal, or lateral; one per areole; unarmed, tubular to funnelform; sessile; medium-sized to large; 3.5–8 cm long; regular. The receptacle shortly but conspicuously produced beyond the ovary into a tubular hypanthium. The pericarpel often naked below the tube. The hypanthial tube not naked; with scales (these small). The axils of the scales of the hypanthial tube not naked (small, short-haired and woolly, often nectariferous). The hypanthial tube spineless. The perianth white, or yellow, or red to pink (commonly rose); limb relatively large. Stamens numerous; adnate to the perianth (inserted in the tube and throat); with the lowermost arising from a receptacular rim more or less covering the nectar chamber.
The mature fruit 2.5–3 cm long (where recorded); ovoid; not naked (with small scales and wool); with persistent floral remains. The seeds numerous, black; pyriform; not encased in bony arils. The testa shiny; smooth, without ornamentation. Cotyledons reduced or vestigial.
Natural Distribution. Southern Mexico.
Classification. 4 species. Subfamily Cactoideae. Tribe Pachycereeae.
Cf. Hunt, 1967.
Images. • Cephalocereus deeringii: Britton & Rose (1920). • Cephalocereus columnatrajani (as Pachycereus): Britton & Rose (1920).
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’.
