Coco de Mer tree in a Sri Lanka botanic garden
The Coco de Mer (Lodoicea maldivica), the sole member of the genus Lodoicea, is a palm endemic to the islands of Praslin and Curieuse in the Seychelles. It formerly also occurred on St Pierre, Chauve-Souris and Ile Ronde (Round Island, an islet near Praslin) in the Seychelles group, but has become extinct on these islands. The name of the genus, Lodoicea, is derived from Lodoicus, the Latinised form of Louis, in honour of King Louis XV of France.
 History and mythology
Formerly the Coco de Mer was known as Maldive Coconut. Its scientific name, Lodoicea maldivica, originated before the 18th century when the Seychelles were uninhabited. In centuries past the coconuts that fell from the trees and ended up in the sea would be carried away eastwards by the prevailing sea currents. The nuts can only float after the germination process, when they are hollow. In this way many drifted to the Maldives where they were gathered from the beaches and valued as an important trade and medicinal item.
Legend has it that sailors who first saw the nut floating in the sea imagined that it resembled a woman's disembodied buttocks. This association is reflected in one of the plant's archaic botanical names, Lodoicea callipyge Comm. ex J. St.-Hil., in which callipyge is from Greek words meaning 'beautiful rump'. Other botanical names used in the past include Lodoicea sechellarum Labill. and Lodoicea sonneratii (Giseke) Baill.
Until the true source of the nut was discovered in 1768, it was believed by many to grow on a mythical tree at the bottom of the sea. European nobles in the sixteenth century would often have the shells of these nuts polished and decorated with valuable jewels as collectibles for their private galleries. The Coco de Mer tree is now a rare and protected species.
The species is grown as an ornamental tree in many areas in the tropics, and subsidiary populations have been established on Mahé and Silhouette Islands in the Seychelles to help conserve the species. The fruit is used in Ayurvedic medicine and also in traditional Chinese medicine.
The Coco de Mer belongs to the Coryphoidae subfamily and tribe Borasseae. Borasseae is represented by four genera in Madagascar and one in Seychelles out of the seven worldwide. They are distributed on the coastlands surrounding the Indian ocean and the existing islands within. Borassus, the genus closest to Lodoicea, has about five species in the "old world," one species in Africa, one in India, South-East Asia and Malaysia, one in New Guinea and two species in Madagascar (Uhl and Dransfield, 1987).
The nut, or fruit without the husk
The Vallée De Mai palm forest in Praslin
The tree grows to 25'34 m tall. The leaves are fan-shaped, 7'10 m long and 4.5 m wide with a 4 m petiole. It is dioecious, with separate male and female plants. The male flowers are catkin-like, up to 1 m long. The mature fruit is 40'50 cm in diameter and weighs 15'30 kg, and contains the largest seed in the plant kingdom. The fruit, which requires 6'7 years to mature and a further two years to germinate, is sometimes also referred to as the Sea Coconut, double coconut, coco fesse, or Seychelles Nut.
The Coco de Mer is the most interesting species of the six monospecific endemic palms in Seychelles since it is the "only true case of island gigantism among Seychelles flowering plants, a unique feature of Seychelles vegetation" (Proctor, 1984). It is one of the most universally well-known plants and holds three botanical records; the largest fruit so far recorded weighed 42 kg; the mature seeds weighing up to 17.6 kg are the world's heaviest (Uhl and Dransfield, 1987; Wise, 1998; Carlstrom, unpublished) and the female flowers are the largest of any palm (Uhl and Dransfield, 1987; Wise, 1998).
Of the six endemic palms it is the only dioecious species, with male and female flowers located on different plants. A selective review of the biology of the species was recently published by Edwards, Kollmann & Fleischmann (2002).
The Coco de Mer palm is robust, solitary, up to 30 m tall with an erect, spineless, stem which is ringed with leaf scars (Calstrom, unpublished). The base of the trunk is of a bulbous form and this bulb fits into a natural bowl, or socket, about 2.5 ft in diametre and 18 inches in depth, narrowing towards the bottom. This bowl is pierced with hundreds of small oval holes about the size of a thimble with hollow tubes corresponding on the outside through which the roots penetrate the ground on all sides, never, however, becoming attached to the bowl; they're partially elastic, affording an almost imperceptible but very necessary "play" to the parent stem when struggling against the force of violent gales.
The crown is a rather dense head of foliage with leaves that are stiff, palmate up to 10 m in diametre and petioles of two to four metres in length. The leaf is plicate at the base, cut one third or more into segments 4'10 cm broad with bifid end which are often drooping. A triangular cleft develops at the petiole base (Uhl and Dransfield, 1987).
The clusters of staminate flowers are arranged spirally and are flanked by very tough leathery bracts. Each has a small bracteole, three sepals forming a cylindrical tube, and a three-lobed corolla. There are 17 to 22 stamens. The pistillate flowers are solitary and borne at the angles of the rachis and are partially sunken in it in the form of a cup. They are ovoid with three petals as well as three sepals (Uhl and Dransfield, 1987). It has been suggested that they may be pollinated by animals such as the endemic lizards which inhabit the forest where they occur (Beaver and Chong Seng, 1992). Pollination by wind and rain are also thought to be important (Edwards, Kollman and Fleischmann, 2002). Only when Locoicea begins to produce flowers is it possible to determine the sex of the plant which can vary from 11 to 45 years or more (Chong Seng, pers.comm. 2006; Andre, pers.comm. 2006).
Male Coco de Mer inflorescence
Inflorescences are interfoliar, lacking a covering spathe and shorter than the leaves. The staminate inflorescence is catkin-like, one to two metres long and generally terminal and solitary, sometimes two or three catkins may be present. The pistillate inflorescences are also one to two metres long unbranched and the flowers are borne on a zig-zagging rachilla (Wise, 1998).
The fruit is bilobed, flattened, 40 to 50 cm long ovoid and pointed, and contains usually one but occasionally two to four seeds. The epicarp is smooth and the mesocarp is fibrous. The endosperm is thick, relatively hard, hollow and homogenous. The embryo sits in the sinus between the two lobes. During germination a tubular cotyledonary petiole develops that connects the young plant to the seed. The length of the tube is reported to reach about four metres (Uhl and Dransfield, 1987). Beaver and Chong Seng (1992) state that in the Vallee de Mai the tube may be up to 10 m long.
The Seychelles nut was once believed to be a sea-bean or drift seed, a seed evolved to be dispersed by the sea. However, it is now known that the viable nut is too heavy to float, and only rotted out nuts can be found on the sea surface, thus explaining why the trees are limited in range to just two islands. As of 2003, it held the record for the world's largest seed.