Elaeocarpus angustifolius
Elaeocarpus angustifolius is a species of flowering plant in the family Elaeocarpaceae that occurs from India to New Caledonia and northern Australia. Common synonyms are E. ganitrus and E. sphaericus. It is a large evergreen tree, often with buttress roots, and has leaves with wavy serrations, creamy white flowers and more or less spherical bright blue edible fruit. In English, the tree is known as utrasum bean tree in India. In Sri Lanka recorded names are woodenbegar and Indian bead tree. It is simply known as elaeocarpus in the Northern Territory of Australia. Other names used for this tree in Australia are Indian oil fruit and genitri. In Hawaii it is known as a blue marble tree.
In India, the cleaned pits of the fruit of this tree are known as rudraksha and are widely used as prayer beads, particularly in Hinduism. Rudraksha might be produced by more than one species of Elaeocarpus; however, E. angustifolius is the principal species used in the making of mala.
Description
According to M.J.E. Coode, Elaeocarpus angustifolius is a tree that typically grows to a height of and usually has buttress roots at the base of the trunk. The leaves are about long, wide with wavy serrations on the edges and tapering to a petiole long, but lacking a pulvinus. Old leaves often turn bright red before falling. The flowers are arranged in racemes up to long, each flower on a pedicel long. The five sepals are long and wide. The five petals are creamy white, egg-shaped to oblong, long and wide, the tip with linear lobes. There are between thirty-five and sixty stamens and the style is long and glabrous. The fruit is a more or less spherical, bright blue or purple drupe in diameter. Note, however, that Coode considered E. grandis to be the same species as E. angustifolius, and the above description applies to both taxa.Mature trees will grow massive buttresses which generally completely encircle the base of the trunk. This may be an adaptation to becoming emergents in some habitats, or often growing in secondary woodland—buttress roots can better distribute tensile stress in the base of the tree transmitted down from wind in the crown. In E. angustifolius the buttresses are thought to develop in response to stresses experienced by the tree during comparatively brief periods of fast development. The buttress wood has a partially different composition than the wood of the trunk.
Fruit
It is an evergreen tree that grows quickly. The tree starts bearing fruit in three to four years.The blue-coloured drupes of the tree contain large stones or pits, which are covered by an outer husk of fruit flesh. This blue colour is not derived from a pigment, but is caused by structural colouration. The fruit weigh 7g on average, but range from 10 to 4g. The stone at the centre of the fruit, technically a pyrena, is typically divided into multiple segments, which are locules, each usually bearing a seed.
Infraspecific variability
No infraspecific forms are recognised. Populations in the periphery of the distribution exhibit a range of morphological characters which do not betray much biogeographical structuring, i.e. individuals can be found in New South Wales which may look almost identical to individuals in Malaysia or Fiji. However, in the centre of the distribution, the islands of Indonesia and in the Malay Peninsula, there are a number of confusingly divergent populations. In general, populations in this area can be divided into two main groups, larger leafed and flowered, and smaller leafed and flowered.A long history of use by man may have confused the issue further. It is possible the long-distance trade has mixed lineages, or influenced the distribution of specific types. The species is often cultivated as an urban street tree in Indonesia and Malaysia. It appears that the larger leafed form is more often selected for planting as a street tree here. This appears to already be the case on Java over a century ago, based on the collection notes accompanying herbarium specimens.
A closer look at the stones used in classic mala garlands also reveals some interesting issues. It is the smaller stones which are traditionally worth the most, and many of the stones in the garlands are only 7mm in diameter, while known stones in museums collected by botanical collectors are all larger, 10mm and up. Not only that, special powers are ascribed to stones with more than the usual five facets, with those having more facets commanding a higher price. Prayer beads with up to 20 facets are known, but botanists have always collected ones with 5–7 facets, rarely 4 or 8. The small size may be due to a special cultivation technique or an as yet unknown race or species, and it is possible there has been some limited selection by people involved in the trade—it is possible that there are, or once were, special cultivars grown for their superior stones. A study of the fruit and stones in Sri Lanka found that variation in characteristics such as size and colour were highly influenced by the individual trees, as opposed to season or location. The authors opine that it is indeed possible that specific individual trees are cultivated for their fruit and stone qualities.
Similar species
It is a widespread and variable species, and many regional populations of E. angustifolius were considered to be different species in the past, but these are at present all considered the same species. An exception is the taxon E. grandis, although it cannot reliably be told apart from the E. angustifolius and was considered the same species by the last Elaeocarpus expert taxonomist, it remains recognised in parts of Australia: plants in Queensland and New South Wales are considered E. grandis, those found growing elsewhere are E. angustifolius. A 2013 PhD thesis by Yumiko Baba which compared a number of genetic sequences of different taxa found that E. grandis was indistinguishable from E. angustifolius in most studied sequences, but that in one sequence with more variety, her two E. grandis samples were found to be within the diversity of E. angustifolius, with the two samples in fact more divergent from each other than from other samples within the E. angustifolius synonymy.E. grandis/angustifolius can, however, be told apart from other species of Elaeocarpus by having petals much divided at the apex; small, round fruit; 5-7 locules per stone; straight embryos; and glabrous leaves with even and fine serrations along their margins. The most similar species in Northern Territory is E. arnhemicus; this species has leaves which are less long and more wide, stamens without bristles, and fruit which are ellipsoid in shape as opposed to round.
Overall, Coode found E. ptilanthus to be the most similar species, and very difficult to tell apart without the fruit. Whereas E. angustifolius is largely a lowland species, E. ptilanthus is found in highlands and cloud forests. Coode notes that the crowns are different, that of E. ptilanthus being dark, dense and umbrella-like, as opposed to light and spreading. The leaves are leathery, darker and shinier on top. The most important difference is seen in the fruit; E. ptilanthus has twice-as-large fruit with fibrous flesh, E. angustifolius is more juicy. The stone is very different in E. ptilanthus, the ornamentation having developed into numerous holes and arches, through which the strong fibres run, making cleaning a stone difficult. These arches are usually flattened and long, and curve towards the apex of the stone. The stone is also shaped differently, it is ellipsoid or ovoid, not round. A study comparing a number of gene sequences, however, found that a E. ptilanthus sample was largely indistinguishable from E. angustifolius, with the exception of one more variable sequence, where it was nested within different E. angustifolius samples.
Taxonomy
Writing from the island of Ambon in the Moluccas in the mid-16th century, the German-Dutch soldier, merchant and botanist Georg Eberhard Rumphius provided the first modern binomial description of the species in his work Herbarium Amboniense, in which he introduced the species to European science as Ganitrus Ganitri. Few ever read the work at the time, as it was considered a trade secret by the V.O.C., and published long after Rumphius had died. When Carl Linnaeus introduced his new standard of taxonomic nomenclature, he missed out on using this work, as he only received his copy after having worked on the 1753 edition of his Species Plantarum. The specific epithet ganitrus was derived from ganitri, the name for this species in Sundanese and Malay.When Linnaeus published his Species Plantarum, he listed only one species of Elaeocarpus, referring it to the 1747 formal description, as well as an illustration, of "Elaiocarpus serrata" given by Johannes Burman in his book Thesaurus zeylanicus. which Linnaeus used as reference in his work.
In 1791, long before the International Code of Botanical Nomenclature rules had been formalised, in his book on the fruits and seeds of plants, Joseph Gaertner renamed the genus from Elaeocarpus to Ganitrus again, arguing that as Rumphius had been the first to formally describe the species, his name should have taxonomic priority. The only species he placed in this genus was G. sphaerica. This is not what is known as 'good species'; it is a frankenstein, composed of the description of Johannes Burman's 1747 Elaiocarpus serrata and an illustration of the fruit and the seeds of Rumphius's Ganitrus Ganitri. Gaertner also cites Linnaeus's Elaeocarpus serratus in the synonymy, which according to the ICBN rules is the only valid taxon name. Some taxonomists believed this invalidates the name altogether, in 1980 the French botanists Christiane Tirel and Jean Raynal stated that because Gaertner had cited Linnaeus's Elaeocarpus serrata, that means that the type was automatically that of Linnaeus's E. serrata. Nonetheless, the International Plant Names Index cites ICBN Melbourne Code Article 52.2 and emphasise that Gaertner "did not cite E. serratus nor its type", although he did cite E. serratus. Because it was built up using at least two species, this name is a synonym pro parte of both species, according to the botanist M.J.E. Coode, an Elaeocarpus expert. Gaertner was not followed in his idea to move the genus to a pre-Linnaean name by most botanists, in the next century a newer crop of botanists described new species of the genus using Linnaeus's name.
For example, the name Elaeocarpus angustifolius was first introduced in 1825 by the again German-Dutch Carl Ludwig Blume in his book Bijdragen tot de Flora van Nederlandsch Indie from material collected in the "mountains of Buitenzorg Province". This name was accompanied by an adequate species description, and a reference to an extant type. As this is the first valid name, i.e. correctly described and effectively published name in the correct genus available in the Linnaean system, this name takes priority as the correct name for the species.