Pilosocereus barbadensis (Britton & Rose) Byles & Rowley (1957: 66)

Hoxey, Paul & Gdaniec, Andrew, 2021, An evaluation of the Cactaceae of Barbados, Grenada, Saint Vincent, and The Grenadines, Phytotaxa 483 (1), pp. 25-74 : 54-58

8. Pilosocereus barbadensis (Britton & Rose) Byles & Rowley (1957: 66) ≡ Cephalocereus barbadensis Britton & Rose (1920: 44) ≡ Pilocereus barbadensis (Britton & Rose) Berger (1929: 156)

Type:— BARBADOS. 30 September 1915, Rose & Russell 21181. [ Britton & Rose (1920: Plate VI, figure 3) shows the top of the type specimen in the New York Botanical Garden in flower in 1916. Britton & Rose (1920: 45, Fig. 65) is from a photograph of the same plant.]

Lectotype [designated by Zappi 1994 (first-step typification); here the second-step typification (Art. 9.17 ex. 14)]:— BARBADOS. 30 September 1915, Rose & Russell 21181 (US0011535!, image of the lectotype available at https://collections.nmnh.si.edu/media/?irn=10283977).

Description:—Plants branching from the base. Stems upright, to 6 meters high, 60–70 mm diameter. New growth light green, older growth bluish green. Ribs 9 –12, 15 mm high, 10 mm wide, rounded shape. Areoles 3–4 mm diameter, white felt, 10–12 mm spacing. Young areoles with a few white hairs. Flowering areoles and non-flowering areoles distinct. Non-flowering areoles, without hairs, spines short, 15–20, about 10–15 mm long, light brown to grey. Flowering areoles, confined to one side of a branch only, with dense tufts of white hairs, spines, 30–40, to 60 mm long, brown, flexible. Flowers nocturnal, 60–65 mm long, 35 mm wide at top of flower tube, recurved petals extend slightly more. Flower tube slightly elongated and thick, greenish yellow, smooth without areoles. Outer perianth segments slightly pinkish. Petals white, slightly pink hue. Style 6–7 cm long, 3 mm wide, extends about 10 mm beyond the flower. Stamens numerous, white, about 20 mm long. Anthers pale yellow, filling upper half of flower tube. Nectar chamber, elongated, 6 mm across by 10 mm deep, slightly pink base. Fruit red, sub-globose, 35 mm in diameter; seeds, shiny black.

Distribution ( Fig. 2J ):— Pilosocereus barbadensis is endemic to Barbados and restricted to the eastern area of Barbados growing on a geological formation called the Scotland District which consists of sedimentary sandstone rocks ( Allen 2017: 208). Note that the other 85% of geological substrate of Barbados are limestone. P. barbadensis is usually found on seaward-facing slopes ( Fig. 34 ).

Discussion:— Franck (2019) considered the plants on Barbados to be Pilosocereus curtisii . However, based on our observations, the Barbados plants should be treated as a distinct, although closely related, taxa. We cannot discount the possibility that P. barbadensis is identical to plants found elsewhere in the Lesser Antilles, or that plants intermediate with P. curtisii exist. If this species is distinct, then it becomes a Barbados endemic, having a very restricted distribution area and hence of conservation concern. We observed that many plants have been damaged by burning and are under threat due to land use change. Maycock (1830: 202) used the misapplied name Cereus monoclonos for this plant. Hughes (1750: 135) describes a plant he calls “The American Torch, Lat. Cereus maximus.”, which is this species.

Compared to Pilosocereus curtisii , P. barbadensis has thicker stems, usually more ribs and a much greater difference between flowering and non-flowering areoles ( Figs. 35–37 ). The flowering areoles often form on just one side of the stem in three or four ribs. We only observed flowers on the mature areoles ( Fig. 38 ) and never juvenile areoles. A comparison of characteristics of the two Pilosocereus species is outlined in Table 6.

Typification of Cephalocereus barbadensis :— Zappi (1994: 151) designated a US specimen (Rose & Russell 21182) as the lectotype. However, there are two specimens with that number (21182) in US. A wood sample ( US 00365367) and a sheet ( US 00115535), the latter one bearing stem fragments, spination, flower and fruit. The designation of a lectotype from a single gathering consisting of more than one specimen must be accepted (Art 9.17) but by using a second step lectotypification we narrow down the type to specimen US 00115535 only .

Specimens examined:— BARBADOS. 30 September 1915, Rose 21181 (NY, US); 12 November 1915, Rose 21181 (NY); 21 February 1924, Miller 236 ( US); 2–3 March 1979, Howard & Howard 18738 (A); 24 March 1981, Gray 3 (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 34. A large branching specimen of Pilosocereus barbadensis (Hoxey 1708.01), Barbados.

FIGURE 35. Non-flowering stem of Pilosocereus barbadensis (Hoxey 1705.01).

FIGURE 36. Flowering stem of Pilosocereus barbadensis (Hoxey 1708.01). Flowering areoles have dense tuft of hairs, with more numerous and much longer spines.

FIGURE 37. Pilosocereus barbadensis (Hoxey 1705.01). A comparison of flowering (top) and non-flowering (below) areoles.

FIGURE 38. Pilosocereus barbadensis (Hoxey 1708.01) in flower.