The genera of Cactaceae

L. Watson and M.J. Dallwitz

Harrisia Britton

Apple cactus.

Including Eriocereus (A. Berger) Riccob., Roseocereus Backeb.

The plants cerioid; not ‘low and very compacted’. The stems spiny; elongate cylindric; neither cephaliate nor pseudocephaliate. The plants terrestrial and self supporting, or scrambling, or climbing; producing aerial roots, or not producing aerial roots; branched (the branches often upright or arching, up to 25 metres long when clambering); prostrate, or erect; shrubby, or tree-like; often with well formed trunks (these slender), or not developing conspicuous trunks; solitary, or clustering; to 1–7 m high (when erect or clambering). The stems not columnar. The branches differing in form from the main stem, or resembling the main stem. The main stem more or less cylindrical. The branches cylindrical, or angled. The stems not segmented; ribbed and grooved (or angled). The ribs 4–12; longitudinal. The grooves wide. The plants conspicuously tuberculate to not conspicuously tuberculate. The tubercles if present, low. The tubercles connected by the ribs; borne in longitudinal series. The areoles associated with tubercles, or not tubercle-associated (then borne on rib prominences); simple. The flowering areoles resembling the non-flowering ones. The areoles without glochids; with spines. The spines clustered; (3–)4–16 (few to many, variable); 0.4–6(–9) cm long; with radials and centrals differentiated, or showing little or no difference between radials and centrals. Central spines when differentiaed, 1–4. Radial spines 4–10. The spines straight (often large and stout). The mature stems leafless.

Flowering at night. The flowers lateral; one per areole, or more than one per areole (?); funnelform; sessile; large; 12–22 cm long (and 8–12 cm in diameter); regular. The receptacle conspicuously produced beyond the ovary into a tubular hypanthium. The pericarpel bearing scales with areoles and hairs or wool, but no bristles or spines. The hypanthial tube slender, as long as or longer than the perianth, not rigid; not S-shaped; not naked; with scales. The axils of the scales of the hypanthial tube not naked (with hairy or woolly areoles). The hypanthial tube spineless. The perianth white; limb relatively large. The perianth segments relatively short, broad; pointed, or apiculate. Stamens numerous; adnate to the perianth (inserted in the tube and throat); not grouped.

The mature fruit 3–8 cm long; usually globose; yellow, or orange, or red; naked, or not naked (the scales and areoles often deciduous); spiny, or without spines; without the persistent style characteristic of Cereus (q.v.); fleshy; dehiscent (splitting at maturity in subgenus Eriocereus), or indehiscent (in subgenus Harrisia). The seeds with deeply impressed hilum areas forming chambers, black; ovoid (? - "broadly oval"); not encased in bony arils; without a mucilage sheath. The testa verrucose. Cotyledons reduced or vestigial.

General anatomy. The vessel end-walls irregularly reticulately perforated, or simple.

Natural Distribution. Florida, throughout the Caribbean, Brazil, Paraguay, Argentina, and H. martinii a noxious weed in other countries.

Classification. About 20 species. Subfamily Cactoideae. Tribe Trichocereeae.

Cf. Hunt (1967).

Images. • Harrisia eriophora: Britton & Rose (1920). • Harrisia fragrans andH. martinii: Britton & Rose (1920). • H. martinii and H. gracilis: Britton & Rose (1920). • Harrisia tortuosa: Britton & Rose (1920). • Harrisia fernowii and H. pomanensis (as bomplandii), with Espostoa melanostele (as Binghamia): Briton & Rose (1920).