Melocactus intortus (Miller) Urban (1919: 35)

Hoxey, Paul & Gdaniec, Andrew, 2021, An evaluation of the Cactaceae of Barbados, Grenada, Saint Vincent, and The Grenadines, Phytotaxa 483 (1), pp. 25-74 : 46-49

5. Melocactus intortus (Miller) Urban (1919: 35) ≡ Cactus intortus Miller (1768 : unpaged) ≡ Echinocactus intortus (Miller) Candolle (1828: 462) .

Type:— ANTIGUA.

Neotype (designated by Taylor 1991: 78):— ANTIGUA. Shirley Heights , 26 July 1977, R.A. Howard 18492 (K000251492!, image of the lectotype available at http://specimens.kew.org/herbarium/K000251492

Description:—Body globose to tapering cylindric, to 70 cm tall and 40 cm diameter. Ribs (9–)14–20(–25). Spines stout, straight, 2–7 cm long, yellow to brownish; central spines 1–3; radial spines 8–11. Cephalium with copious white wool and soft red-brown bristles, cylindrical with age, reaching 1 m long in exceptional cases. Flowers pink, small, barely emerging from the cephalium, 15–20 mm long, style pink. Fruit oblong to clavate, pink-reddish, 20–25 mm. Seeds black.

Distribution in the study area ( Fig. 2E ):— Only found on Union island and the adjacent Frigate island, so expanding its distribution area, southwards by 135 km from Saint Lucia.

General distribution:— The accepted distribution of Melocactus intortus is from Saint Lucia, northwards in the Lesser Antilles and continuing to the Bahamas, Virgin islands, Puerto Rico and as far as the Dominican Republic with Melocactus intortus subsp. domingensis Areces (1997: 246) .

Discussion:— This disjunct population of Melocactus intortus at Union and Frigate islands was quite unexpected and gave us the biggest surprise of the expedition. These plants, shows several differences with the similar M. broadwayi . Firstly, the seedling plants are more robust and deeper brown spination ( Fig. 20A ) compared to those of M. broadwayi which display shorter and lighter coloured spines ( Fig. 20B ). The adult plants showed further differences such as larger stems, straight, more robust spination and with a cephalium that elongates with age ( Figs. 21–22 ). A final and most important difference was observed in the flowers ( Fig. 23 ), which are much smaller than M. broadwayi with shorter petals that only just emerge from the cephalium and have pink stigma-lobes (white in M. broadwayi ).

A more detailed survey of Union Island is however required to clarify if Melocactus broadwayi also occurs there. Note that plants of M. intortus without both flowers and elongated cephalium can easily be confused with M. broadwayi . M. intortus usually has thicker and straighter spination, but differences are not always clear. Very careful examination of the plants is required and the most effective way to distinguish between the two species is to observe the flowers (see Table 5).

The genus Melocactus is not currently known from Barbados, but Hughes (1750: 136 & 226) wrote two descriptions for a plant he called “The Turk’s Head”. This vernacular English name is still in use today to refer to Melocactus species. The first entry is given the Latin name “ Melocactus Americanus ” and the second “ Melocactus Americana major”. The Latin name “ Melocactus americanus ” at first sight appear to be a valid binomial, but is not because this work predates the start of botanical nomenclature (1 May 1753). Both descriptions are good and clearly apply to a Melocactus species. It is not obvious why Hughes (l.c.) thought there were two distinct taxa but perhaps the “major” word simply refers to larger plants. He fortunately provided some measurement for these plants, which he states are 1 foot (= 30 cm) tall and 2 feet (= 60cm) in circumference (= 20 cm in diameter). He continues and says the spines are about 1 inch (= 2.5cm) long and the cephalium is 8 inches (= 20 cm) long, and 3 inches (= 7.6 cm) in diameter and of a snuff (dark yellowish-brown) colour. This description corresponds with M. intortus , especially the elongated cephalium, which is a feature of this species. We believe that this is the most likely identity of these plants, but unfortunately, we will never know with certainty, as neither herbarium material nor contemporary observations exist. Maycock (1830: 201) lists this species as Melocactus communis and we assume it was present at that time, but it is not included in Gooding et al. (1965). It is now assumed to be extinct on Barbados and probably has been for some time.

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 20. A comparison of Melocactus seedlings. A. Melocactus intortus (Hoxey 1677.01, Frigate Island, south of Union Island). B. Melocactus broadwayi (Hoxey 1662.02, Bequia).

FIGURE 21. Mature Melocactus intortus (Hoxey 1677.01) with elongated cephalium about 25 cm tall, on Frigate Island, south of Union Island.

FIGURE 22. Melocactus intortus (Hoxey 1675.02) with robust straight spination, Union Island.

FIGURE 23. Melocactus intortus (Hoxey 1676.01) with small pink flowers just emerging from the cephalium, Union Island.