Materia Medica, Pharmacology & Bio-Prospecting

The Bilak Tree (Aegle marmelos)

One of the plants Georg Eberhard Rumphius (1627-1702) encountered during his time in Indonesia was, as he describes it in The Ambonese Herbal, a tree similar in height to a lemon tree with a trunk as “thick as a man, covered with gnarls and pits” (Rumphius 2011, 505). Two to three branches reach outward from the trunk of this tree, each supporting a multitude of smaller branches. Leaves dot these branches. As a result, this tree sports a voluminous crown (the “head” of the tree). Rumphius refers to this plant as the Bilak tree, which is comprised of 3 closely related species: bilac carbau/carbou, bilac telloor (the most common variety), and bilac pissang (Rumphius 2011, 505).

Rumphius did not come up with this subdivision independently – his classifications were heavily informed by local plant relationship frameworks (Merrill 1917, 41). Ethnographic research on the local (Ambonese) and nearby Southeast Asian cultures were likely a source of inspiration for Rumphius’ distinction between the different Bilac subspecies. Rumphius’ ethnographic research indicates that Ambonese people in the 17th century differentiated between the varieties stipulated above (bilac carbou, bilac telloor, and bilac pissang), using each for different purposes. In Amboina, bilac telloor was commonly eaten, while bilac carbou was used for poisoning fish. Usage of a given subspecies varied between different Southeast Asian nations: “the Javanese and Balinese eat the raw fruit [of bilac telloor] with gusto, but our nation [Amboina] does not find it quite so agreeable” (Rumphius 2011, 506). In Amboina, it was common practice to roast the fruit before consumption, in order to decrease the sliminess and strong flavors of the fruit. Bilac carbou, though not often eaten in Amboina, was eaten in Java and Ceylon (modern day Sri Lanka) (Rumphius 2011, 509).

Rumphius also investigated the medicinal properties of the Bilak tree. He mentions the work of botanist “Jacob. Bont.”, who noted this plant’s (which Bont. refers to as “Malum Cydonium Indicum” or “Slymappels”) medicinal properties (Rumphius 2011, 506). The sap can be used to combat thrush, while the roasted fruit can be used to treat dysentery and cholera. In more recent years, these observations have been verified through biomedical studies. In addition to combatting thrush, cholera, and dysentery, studies have also identified Aegle marmelos as having anti-diarrheal, pro-digestant, anti-inflammatory, anti-parasitic, and anti-anclyostomiasis properties (Buenz et al. 2005, 63–64).

Though the medicinal properties cited by Rumphius mirror recent studies, Rumphius’ classification of the Bilak tree is discordant with that used today. Approximately 225 years after Rumphius’ publication of the first half of The Ambonese Herbal, E.D. Merrill, a botanist working in Indonesia, sought to analyze and classify the plants in Rumphius’ work. E.D. Merrill’s classification, which is the one commonly adapted today, collapses these 3 species into 1 species: Aegle marmelos (Rumphius 2011, 505).

Of importance in botany works, past and present, are the illustrations and/or photographs (dependent on available technology) included in the work. These visualizations serve as important references for those who wish to identify the plant in the future. E.D. Merrill makes several observations about The Ambonese Herbal’s illustrations – which, it is important to note – were ultimately not done by Rumphius, as he had become blind during the production of the final draft. Rumphius had done original drawings for earlier versions, but those were destroyed in a fire (Buenz et al. 2005, 58). First, flowers and fruit (among other parts of particular interest to European botanists) were illustrated disproportionately large. Second, Rumphius’ classification style heavily integrated local plant relationship frameworks. The local framework put emphasis on certain key characteristics, such as leaf appearance; wood appearance; presence/absence of latex; and the taste and smell of leaves, flowers, and fruit (Merrill 1917, 41).

The other depiction of Aegle marmelos shown on this page was created by Marianne North in 1878, during her time in India. European botanists in India, the native land of Aegle marmelos, often referred to this plant as “Bael”, a term which is still commonly used today. Marianne North travelled solo around the world, which was unheard of for Victorian women of the time. Her painting style was also unconventional – she used oil paints that were thick and vibrant, as opposed to the traditional opaque watercolors (McHale 2020).

In both of these depictions of Aegle marmelos, the illustrators pay special attention to the fruit. Perhaps this is due to the practicality of the fruit – the fruit of Aegle marmelos can be eaten. From Rumphius' The Ambonese Herbal, it seems as if the other parts of Aegle marmelos do not have much practical use.

However, there are also clear differences in depictions of this plant. In The Ambonese Herbal, the leaves are depicted as very scalloped along the edges, while the scallops in North's painting are more subdued. The illustration from The Ambonese Herbal employs shading to create dimension and mimic the way in which natural light would illuminate the plant. North's painting is the more life-like of the two. Her image is created through extensive layering and blending of different colors in order to capture color complexities.

Differences in representation boil down to the fact that there are different illustrators in different cultural contexts, with different stylistic norms and ideals. The Ambonese Herbal illustrations were commissioned by the Dutch Rumphius, but drawn by Ambonese locals. As such, the illustrations in The Ambonese Herbal are likely a blend of Dutch conventions (Rumphius' instructions) and also Indonesian art styles of the 17th century. North’s image was likely informed by the culture of 19th century England. At the same time, she likely had other influences (perhaps her own innate sense of unconventionality), as her vibrant oil paintings were not considered conventional in 19th century England.

Aegle marmelos is a plant that captured the attention of European botanists bioprospecting in Southeast Asia throughout the 17th century and beyond. This plant is still a source of inspiration today, both for those who utilize it as part of their everyday culture, and to scientists, who continue to identify medicinal and biochemical properties of interest.


Buenz, E.J., H.E. Johnson, E.M. Beekman, T.J. Motley, and B.A. Bauer. 2005. “Bioprospecting Rumphius’s Ambonese Herbal: Volume I.” Journal of Ethnopharmacology 96 (1): 57–70.
Kew Science: Plants of the World Online. n.d. “Aegle marmelos."
McHale, Ellen. 2020. “Things You Should Know about Marianne North.” Royal Botanic Gardens, Kew.
Merrill, E.D. 1917. An Interpretation of Rumphius’s Herbarium Amboinense. Manila: Bureau of Science.
Rumphius, Georgius Everhardus. [1743] 2011. The Ambonese Herbal. Translated by Eric Montague Beekman. New Haven: Yale University Press & National Tropical Botanical Garden.

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