| | The genera of Cactaceae |
Giant Saguaro.
The plants cerioid; not ‘low and very compacted’. The stems spiny; elongate cylindric. The plants branched; erect; large, tree-like; to 16 m high. The stems columnar. The main stem more or less cylindrical. The branches cylindrical. The stems not segmented; 12–30 ribbed and grooved. The ribs longitudinal. The plants not conspicuously tuberculate. The areoles very numerous and closely spaced along the ribs, borne in longitudinal series; simple (the flowering ones more or less continuous and densely felted with clustered spines, the non-flowering ones with a single, longer central spine). The flowering areoles differing in form from the non-flowering ones. The areoles with spines. The spines densely clustered; 15–30; 2.5–3.8 cm long; at least in the non-flowering areoles with radials and centrals differentiated; stiff; diverging, straight; terete; grey to blackish. The mature stems leafless.
Flowering at night and during the day. Pollination entomophilous, ornithophilous, and cheiropterophilous; via hymenoptera (e.g., bees). The flowers more or less terminal to lateral (arising near the stem tips); more than one per areole; tubular to funnelform; sessile; large; 8.2–12.5 cm long; regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium. The pericarpel pericarpel covered with distinct scales and felted areoles. The hypanthial tube not naked; with scales. The axils of the scales of the hypanthial tube not naked (felted). The hypanthial tube spineless. The perianth obscured by the tube during bud development (see illustration); white; limb relatively large. The perianth segments short, widely spreading. Stamens very numerous, estimated by Bessey (1914) at almost 3,500 in a single flower; adnate to the perianth (inserted in the throat and tube).
The mature fruit 5–7.5 cm long; ovoid; red; at maturity fleshy (edible); dehiscent; dehiscing vertically by more than one slit (along 3–4 lines). The seeds 2 mm long; with truncate hilum, shiny black; pyriform (obovoid); not encased in bony arils. Cotyledons reduced or vestigial.
Natural Distribution. Arizona and southern California south into Mexico.
Classification. 1 species (C. gigantea). Subfamily Cactoideae. Tribe Pachycereeae.
Cf. Hunt, 1967.
Images. • Carnegiea gigantea: Britton & Rose (1920). • Carnegiea gigantea: © Zoya Akulova (2017). • Carnegiea gigantea: © Zoya Akulova (2017). • Carnegiea gigantea: © Zoya Akulova (2017).
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’.
