Judul: Tribe Colocasieae (Araceae) in Indonesia
Abstrak: Colocasieae Engler is one of the members of Araceae family which has high economic value. In Malesia, especially in Indonesia Colocasieae consist of 3 genera, Remusatia, Colocasia and Alocasia. Study of Araceae especially on the relationship among members of Colocasieae is still poorly known. A total number of 295 specimens deposited in Herbarium Bogoriense (BO), Singapore Herbarium (SING), Bogor Botanical Garden Herbarium and recent collections from several locations in Indonesia such as Mount Wilis (East Java), Mount Watuwila and Natural Forest Ulungolaka (South East of Sulawesi) and Gunung Leuser National Park, Ketambe (Sumatra, Aceh) were examined using morphological approach. 20 species of Colocasieae are known from Indonesia, consisted of 17 species of Alocasia, two species of Colocasia and one species of Remusatia. The presence of Alocasia flemingiana and Remusatia vivipara in several islands in Indonesia is newly reported. Phylogenetic analysis using Maximum Parsimony indicated that each genus is monophyletic. Alocasia is more closely related to Colocasia while Remusatia forms a different clade. The grouping some species in Alocasia clade supports Hay’s 1991 and 1998 group, although these grouping are not supported by high bootstrap value. The lack of phylogenetic signal in morphological data shows the need for additional informative data, such as molecular data for revealing more robust phylogenetic relationships.
Keyword: Colocasieae, Alocasia, Colocasia, Remusatia, Indonesia

Judul: Revision of Calamus and Daemonorops (Arecaceae) in Sulawesi
Abstrak: The rattans of Sulawesi presented by three different genera Calamus, Daemonorops and Korthalsia. Calamus and Daemonorops belong to subtribe Calaminae whereas Korthalsia belongs to subtribe Korthalsiinae. In Sulawesi Calamus is the biggest rattan genus with the number of species more than 23. This genus is very common tropical genus with the centre of diversity is in South East Asia. In Sulawesi Daemonorops consist of 7 species, whereas Korthalsia has one species only that is K. celebica, endemic species to Sulawesi. Recently the biodiversity of Sulawesi has been under severe threats caused by increasing large scale deforestation projects. Many commercial rattans has been illegally harvested and used as raw material for rattans industry. This alarming fact has ecological impact to the rattans of Sulawesi in the form of imminent massive of biodiversity lost. This situation is very true especially for the rattans because almost all species are climbers and they need trees to support their existence. With the intention to minimize the thread to the existence of the rattans of Sulawesi, basic study on the rattans taxonomy is needed as well as accurate documentation. Definite species delimitation is essential to be studied as the diversity continuously under threats and decreased.
Keyword: Sulawesi, Calamus, Daemonorops, Korthalsia, Korthalsia celebica

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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