| | The genera of Cactaceae |
~ Trichocereus, cf. Hunt (1967)
The plants dwarf cerioid, or condensed-cactoid (ostensibly); low and very compacted in their entirety, or not ‘low and very compacted’. The stems spiny; globose, or barrel-shaped to shortly cylindric; 1–5 cm in diameter; not apically depressed; neither cephaliate nor pseudocephaliate. The plants terrestrial and self supporting, or geophytic (almost); mostly basally branched, or offsetting; erect; solitary, or clustering; to 0.02–0.08 m high. The main stem globose, or more or less cylindrical. The branches cylindrical, or globose; to 2–8 cm long; 1–5 cm in diameter. The stems not segmented; more or less ribbed and grooved. The ribs 8–15; longitudinal (sometimes wavy); from scarcely deveoloped to 3 mm high. The grooves wide. The plants more or less conspicuously tuberculate. The tubercles large and nipple-like, or developing ultimately from slight notches. The tubercles connected by the ribs; borne in longitudinal series. The areoles associated with tubercles; closely approximating, or distant. The components of adjacent areoles so extensively covering the mature plant body as to obscure any ribs or furrows, or not obscuring details of the plant body. The areoles borne in longitudinal series; round to elongate simple; woolly; with spines. The spines clustered (often radiating); 3–35; 0.1–1.5 cm long; usually with radials and centrals differentiated. Central spines 4–40. Radial spines 15–25. The mature stems leafless.
Flowering at night. The flowers lateral; one per areole; broadly funnelform; sessile; medium-sized to large; 6–8 cm long; regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium. The hypanthial tube long and slender; not naked; with scales (these acute). The axils of the scales of the hypanthial tube hairy, not naked. The hypanthial tube spineless. The perianth white. The perianth segments relatively short, broad; pointed. Stamens not grouped.
The mature fruit of P. bieblii, 0.6–1 cm long; globose, or pyriform; of P. bieblii not naked (with scales and hairs); without spines. The seeds not encased in bony arils. Cotyledons reduced or vestigial.
Natural Distribution. Southern Peru.
Classification. 3 species. Subfamily Cactoideae. Tribe Trichocereeae.
Images. • Pygmaeocereus beiblii: © Zoya Akulova (2017). • Pygmaeocereus bylesianus: © Zoya Akulova (2010).
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’.
