| | The genera of Cactaceae |
The plants succulent; cerioid to condensed-cactoid; low and very compacted in their entirety to not ‘low and very compacted’. The plants’ appearance dominated by crowded interlacing areolar structures obscuring any tubercles, ribs or furrows. The stems very spiny; ovoid, or barrel-shaped, or shortly cylindric; not apically depressed. The plants unbranched (or sparingly sprouting from the base); erect; solitary; to 1.5 m high. The stems shortly columnar (eventually), or not columnar. The stems not segmented; many ribbed and grooved. The ribs 15–20 (‘as many as 30’); borne spirally (?); broad basally, to 1 cm high. The grooves wide. The plants conspicuously tuberculate (at first). The tubercles connected by the ribs (the areoles becoming confluent); spirally disposed (?). The areoles initially associated with tubercles; closely approximating (at first), or confluent (later). The confluent areoles terminating the stems to lateral. The components of adjacent areoles so extensively covering the mature plant body as to obscure any ribs or furrows. The areoles spirally disposed (?); simple. The flowering areoles often differing in form from the non-flowering ones (often bearing several long brown bristles as well as spines). The areoles with bristles (the flowering ones), or without bristles; with spines. The spines clustered; 9–11; 2–7 cm long (2–3 cm on sterile areoles); with radials and centrals differentiated (or the single central one absent). Central spines 0, or 1. Radial spines 8–10. The spines uneven, tortuous or curved; reddish. The mature stems leafless.
Flowering during the day. Pollination ornithophilous (by Hummingbirds). The flowers lateral (but arising near the apex); one per areole; hairy, slender, tubular; sessile; small to medium-sized; somewhat irregular (curved and bilaterally symmetrical, i.e. slightly zygomorphic). The receptacle conspicuously produced beyond the ovary into a tubular hypanthium. The hypanthial tube curved; curved above the ovary, but not S-shaped; not naked; with scales (covering it). The axils of the scales of the hypanthial tube not naked (hairy). The hypanthial tube spineless. The perianth unexpanding, with short erect segments; red (scarlet). The androecium including staminodes (the nectar chamber being plugged with dense staminodial hairs arising from a thick collar near the base of the tube). Stamens adnate to the perianth (inserted in the throat and tube); separated from the perianth by a conspicuous ring of hairs; and style long exserted beyond the perianth (the filaments red). The stigma lobes yellow.
The mature fruit globose; not naked; with tufts of short, hairlike spines; non-fleshy when mature; dehiscent; dehiscing vertically by one slit (down one side). The seeds black; not encased in bony arils. The testa shiny to dull; puckered and irregularly pitted. Cotyledons reduced or vestigial.
Natural Distribution. Argentina.
Classification. 1 species (D. rhodacantha). Subfamily Cactoideae. Tribe Trichocereeae.
Cf. Hunt, 1967.
Images. • Denmoza rhodacantha: © Zoya Akulova (2018). • Denmoza rhodacantha: © Zoya Akulova (2007). • Denmoza rhodacantha, with Ariocarpus kotschonbeyanus, Pediocactus simpsonii and Eriosyce subgibbosa (as Neoporteria): 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’.
