Pilosocereus curtisii (Otto) Franck (2019: 161)

Hoxey, Paul & Gdaniec, Andrew, 2021, An evaluation of the Cactaceae of Barbados, Grenada, Saint Vincent, and The Grenadines, Phytotaxa 483 (1), pp. 25-74 : 50-54

7. Pilosocereus curtisii (Otto) Franck (2019: 161) ≡ Cereus curtisii Otto (1833: 365) ≡ Pilocereus curtisii (Otto) Salm-Dyck (1845: 24) .

Type:— GRENADA (not known to have been preserved).

Lectotype (designated by Howard 1989: 419):— GRENADA. [icon] t. 3125 in Curtis & Hooker (1832) ( Fig. 28 ).

Description:—Plants much branched from near the base with a short woody trunk. Stems erect, to 3–4(–5) m tall in sheltered localities, 1–3 m in more exposed localities, 30–50 mm diameter, green (never blue or glaucous) ( Fig. 29 ). Ribs 7–8(–9), 10 mm wide and tall. Areoles round, 2–3 mm diameter, white felt, spacing about 10 mm. Young areoles with a few white hairs. Non-flowering areoles with 10–12 spines, 10–20 mm long, very light brown, radial and central spines weakly differentiated. Flowering areoles sometimes with a small but dense tuff of white hairs but often absent (as is the case with the lectotype illustration), spines brown, 12–15, 30– 60 mm long. Flower nocturnal, musty odour, 60 mm long, 40 mm wide at top of the flower tube, recurved petals extend slightly further. Flower tube short and thick, greenish yellow, smooth with a few fleshy scales without areoles. Outer perianth segments slightly pinkish. Petals white, 10 mm wide by 15 mm deep, rounded top, recurved when fully open after dusk. Style 60 mm long, 3 mm wide, extends about 10 mm beyond flower. Stamens numerous, white, about 15–20 mm long, Anthers pale yellow, filling upper half of flower tube. Nectar chamber 10 mm across by 6 mm deep, slightly pink base. Fruits depressed-globular, 50–60 mm across, 40–50 mm deep, deep red, persistent dried flower remains, often split open at maturity. Red pulp with many black shiny seeds.

Distribution ( Fig. 2G ):— Pilosocereus curtisii occurs on Grenada, Saint Vincent and The Grenadines. Franck’s (2019) concept of this species encompasses plants found in a wider area throughout the Lesser Antilles, including Barbados. We however disagree with the occurrence of P. curtisii on Barbados (see next entry for Pilosocereus barbadensis ) but cannot yet comment on plants found elsewhere in the Lesser Antilles.

Discussion:— All Pilosocereus taxa of the Lesser Antilles have been included under the name Pilosocereus royenii ( Linnaeus 1753:467) Byles & Rowley (1957:67) by Howard (1989: 416), Zappi (1994: 153), and Hunt et al. (2006: 241). However, as noted by Zappi (l.c.) the protologue lacks information on reproductive parts and the origin of the type material. The identity of the Linnaeus’ name is uncertain.

Franck (2019: 161) reported Cereus curtisii Pfeiffer (1837: 81) as the basionym for Pilosocereus curtisii . However, a homonym name was validly published few years earlier by Otto (1833: 365). Otto’s name appears without a description, but the citation to the earlier description and illustration by Curtis & Hooker (1832: fig. 3125) make it as validly published according to the Art. 38.1 of ICN. Franck (l.c.) has therefore wrongly cited the basionym for Pilosocereus curtisii , but under Art. 41.8c of ICN, his combination is valid.

Pilosocereus curtisii was the most frequently encountered cactus species we found in Grenada, Saint Vincent, and all The Grenadines. Plants were found in bud, flower, and fruit in most of the populations. Howard (1952: 106), using the name Cephalocereus nobilis ( Haworth 1812: 179) Britton & Rose (1909: 418) for this taxon, stated it is of “infrequent occurrence”, which is not consistent, however, with our observations. The populations on Saint Vincent are restricted to the driest part of the island, on south-western coastal areas. P. curtisii is more widespread on Grenada but again restricted to coastal habitats. Elsewhere in The Grenadines it occurs more frequently, growing usually on sunny rocky areas, whereas the larger plants occur in dry deciduous woodland where they are protected from strong winds. No significant morphological variation was observed in P. curtisii between Grenada, Saint Vincent, and the intermediate islands populations.

On Mayreau we observed a bird eating the fruits of Pilosocereus curtisii and this is obviously a very successful dispersal mechanism, explaining the widespread distribution of this species. Remarkably, we observed healthy populations of plants on several rusting ship wrecks ( Fig. 30 ) which must have been seeded in this way and illustrate how adaptable this species can be.

Areoles on immature stems of Pilosocereus curtisii have small spines and a few hairs on the areoles ( Fig. 31 ). Fully mature flowering areoles have a few more spines which are longer and often have a dense tuff of hair ( Fig. 32 ). There are many stems with areoles of intermediate characteristics. Flowers can form on any type of areole including juvenile examples ( Fig. 33 ). The lectotype illustration also shows such a plant, flowering from a juvenile areole.

Specimens examined:— GRENADA. 10 March 1902, Brown s.n. (K); Carriacou, 7–25 March 1950, Howard 10892 (GH); 24 February 1920, Britton & Hagen s.n. (NY, US); 1 May 1905, Broadway 1766 (NY, GH); 15–25 July 1951, Croizat s.n. (NY); 7 March 1924, Miller 3 ( US); 27 March 1977, Howard 18284 (A); 16 Jun 2001, Hawthorne, Cable & Jules 548 (FHO) . ST. VINCENT & THE GRENADINES. Bequia , 20 March 1977, Howard 18242 (A) ; St. Vincent, 25 May 1947, Morton 6167 ( US) ; St. Vincent, 30 October–11 December 1957, Proctor 16787 (A) .

Figures

FIGURE 2. Distribution of cacti on Barbados, Grenada, Saint Vincent and the Grenadine islands based on observations by the authors. A. Acanthocereus tetragonus. B. Cereus repandus. C. Mammillaria mammillaris. D. Melocactus broadwayi. E. Melocactus intortus. F. Opuntia dillenii. G. Pilosocereus curtisii H. Selenicereus plumieri I. Opuntia dillenii (Barbados). J. Pilosocereus barbadensis (Barbados).

FIGURE 28. Lectotype illustration of Cereus curtisii (≡Pilosocereus curtisii) (Curtis & Hooker 1832: t. 3125). Note the flower emerges from an areole without a tuff of hair.

FIGURE 29. A typical large branching specimen of Pilosocereus curtisii (Hoxey 1703.02) on Sandy Island, Grenada.

FIGURE 30. Pilosocereus curtisii growing on a rusting wreck off the coast of Carriacou.

FIGURE 31. Non-flowering stem of Pilosocereus curtisii (Hoxey 1653.01), Saint Vincent.

FIGURE 32. Flowering stem of Pilosocereus curtisii (Hoxey 1688.02) with copious hairs in the flowering areoles, Carriacou.

FIGURE 33. Pilosocereus curtisii (Hoxey 1659.01) flowering from a naked areole, as also shown in the lectotype illustration. Bequia