| | The genera of Cactaceae |
Barrel cactus.
Including Brittonrosea Speg., Echinofossulocactus Lawr., Homalocephala Britton & Rose
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; discoid to shortly cylindric; apically depressed, or not apically depressed; pseudocephaliate, or cephaliate to pseudocephaliate (with a dense development of wool at the top, in which the flowers develop). The plants branched, or unbranched, or offsetting; erect; solitary, or clustering; to 0.1–2.5 m high. The stems not segmented; ribbed and grooved. The ribs (5–)10–30(–60); few to many, longitudinal; narrow. The grooves fairly wide. The plants conspicuously tuberculate to not conspicuously tuberculate. The tubercles neither grooved nor ridged adaxially. The tubercles when present, connected by the ribs; borne in longitudinal series. The areoles associated with tubercles to not tubercle-associated; distant to closely approximating, or confluent. The confluent areoles terminating the stems. The components of adjacent areoles so extensively covering the mature plant body as to obscure any ribs or furrows (E. polycephalus), or not obscuring details of the plant body. The areoles simple; not associated with extra-floral nectaries; woolly; without glochids; fiercely with spines. The spines clustered; 6–15; 2.5–10 cm long; usually with radials and centrals differentiated. Central spines 1, or 3–5. Radial spines 5–11. The spines stiff; mostly straight. The mature stems leafless.
Flowering during the day. The flowers solitary, or aggregated; terminal; one per areole (but the areoles often more or less confluent and densely woolly towards the upper part of the plant); shortly funnelform, or tubular, or campanulate; sessile; small to medium-sized; 4–7 cm long (and in diameter); regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium to scarcely produced beyond the ovary. The pericarpel with numerous narrow, pointed or spine-tipped scales and densely woolly areoles. The hypanthial tube very short, in some species scarcely produced beyond the ovary; not naked; with scales (these narrow, acuminate). The scales of the hypanthial tube spine-tipped, or not spine-tipped. The axils of the scales of the hypanthial tube more or less naked ((Echinofossulocactus)), or not naked (then densely felted). The hypanthial tube spineless. The perianth petaline, or of ‘tepals’ (with the outer members often with spinescent tips); usually yellow, or red (rarely reddish), or white, or white and purple. The perianth segments more or less erect to spreading. Stamens very numerous; free of the perianth to adnate to the perianth (inserted in the tube, or, where the latter is negligible, around the base of the style); not exserted.
The mature fruit 1.2–7 cm long; ellipsoidal (or oblong), or turbinate; green (-ish), or yellow (-ish), or red; not naked (apically with dense wool and scales, naked below but basally copiously surrounded by wool); without spines; with persistent floral remains; non-fleshy when mature; dehiscent, or indehiscent (thin walled). The seeds 2.8–4 mm long; relatively large, brown, or black; globose or sub-globose to ovoid, or pyriform; more or less compressed; not encased in bony arils. The testa verrucose, or rugose, or pitted, or smooth, without ornamentation. Cotyledons reduced or vestigial.
Natural Distribution. California, Texas to central Mexico. North America and Central America.
Classification. 6 species. Subfamily Cactoideae. Tribe Cacteae.
Cf. Hunt, 1967.
Images. • Echinocactus texensis (as Homalocephala), with Gymnocalycium platense and G. schickendantzii: Briton & Rose (1922). • Echinocactus albatus (as Echinofossulocactus): © Zoya Akulova (2016). • Echinocactus albatus: © Zoya Akulova (2016). • Echonocactus ingens (cf. E. platyacanthus): © Zoya Akulova (2014). • Echonocactus ingens (cf. E. platyacanthus): © Zoya Akulova (2014).
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’.
