Judul: Diversity of epiphytic ferns and Its host in Campus Darmaga of Bogor Agricultural University, West Java
Abstrak: Paku epifit merupakan kelompok tumbuhan paku yang unik, hidup menempel di permukaan pohon inang tanpa merusaknya. Paku epifit memanfaatkan pohon inang sebagai tempat untuk memperoleh kondisi lingkungan tertentu, sementara nutrisi dan air diperoleh dari deposit yang berada di sekitar permukaan pohon inang. Kampus IPB Darmaga memiliki jenis pohon yang beragam dengan kondisi lingkungan yang lembab, sehingga memungkinkan ditemukannya jenis tumbuhan paku epifit yang beragam. Penelitian ini bertujuan untuk mengetahui keanekaragaman tumbuhan paku epifit dan pohon inangnya beserta faktor-faktor yang mempengaruhinya di kawasan kampus IPB Darmaga- Bogor. Penelitian dilakukan di kawasan kampus IPB Darmaga dengan mengumpulkan spesimen tumbuhan paku epifit dan mencatat karakteristik permukaan pohon inang. Data yang diperoleh kemudian dikelompokkan berdasarkan jenis tumbuhan paku dan jenis pohon inang yang ditempati. Faktorfaktor yang mempengaruhi keberadaan tumbuhan paku dianalisis menggunakan analisis Regresi dan Principal Component Analysis (PCA). Sebanyak 22 jenis paku epifit dan 25 jenis pohon inang ditemukan. Jenis tumbuhan paku yang dominan ialah Davalia denticulata (26,59%), Asplenium nidus (25,99%), Vittaria ensiformis (22,97%), Drymoglossum pilloselloides (20,55%), dan Nephrolepis falcata (20,55%). Jenis pohon inang yang dominan ditempati oleh paku epifit ialah pohon kelapa sawit (Elaeis guineensis). Faktor yang mempengaruhi keanekaragaman jenis paku epifit ialah kekasaran permukaan kulit pohon dan posisi paku pada batang pohon, Epiphytic ferns live attaching on its host without damaging it. Epiphytic ferns use the host to obtain certain environmental condition while nutrients and water obtained from deposits around the host surface. Campus Darmaga of Bogor Agricultural University has various tree species and environmental conditions that suitable for the growth of epiphytic fern. The aim of this study was to describe the diversity of epiphytic ferns and its host in Campus Darmaga of Bogor Agricultural University. The study was conducted in Campus Darmaga of Bogor Agricultural University by collecting the speciments of epiphytic ferns and recording the characteristic of tree stem surface. Data was analyzed using Regression Analysis and Principal Component Analysis (PCA). There are 22 species of epiphytic ferns and 25 species of tree hosts. The dominant species of ferns are Davalia denticulata (26,59%), Asplenium nidus (25,99%), Vittaria ensiformis (22,97%), Drymoglossum pilloselloides (20,55%), and Nephrolepis falcata (20,55%). The dominant host is Elaeis guineensis. The diversity of ferns in Campus Darmaga were affected by the roughness of tree surface and the position of ferns on the tree trunk.
Keyword: paku epifit, pohon inang, keanekaragaman, kulit pohon, posisi paku

Judul: Diversity of Reproductive Structures in Epiphytic Ferns in the Campus Area of IPB, Dramaga, Bogor
Abstrak: Institut Pertanian Bogor merupakan kampus dengan biodiversitas tinggi. Tumbuhan paku epifit menjadi salah satu tumbuhan yang sangat melimpah jumlah dan jenisnya, tetapi informasi struktur reproduksinya masih terbatas. Penelitian ini bertujuan mengkarakterisasi struktur reproduksi tumbuhan paku epifit yang tumbuh di kawasan kampus IPB, Dramaga, Bogor. Metode penelitian terdiri dari koleksi sorus, pengawetan dengan alkohol 70%, pengamatan menggunakan mikroskop majemuk yang dihubungkan pada kamera optilab, dan pengukuran menggunakan aplikasi imageRaster v2.1. Tumbuhan paku epifit yang diamati bervariasi pada susunan dan letak sorus serta ciri sporanya. Sorus berbentuk bulat dan garis. Sebagian besar sorus terletak pada tepi daun. Sebanyak 22 jenis tumbuhan paku yang memiliki spora bentuk monolete dengan laesura garis, satu jenis bentuk bulat, dan satu jenis bentuk tetrahedral-globose dengan laesura triradiate. Ukuran spora yang dijumpai yaitu medium, besar dan sangat besar. Semua spora memiliki nilai rasio P/E ≤1,00 dengan tipe peroblate, oblate, suboblate, oblate bulat dan prolate bulat. Permukaan perispora sangat beragam yaitu alate-angular, globules, shallow verrucae, verrucate, echinulate, tuberculate, rugate, globules, echinate, laevate, cristate, regulate, colliculate, granulose, dan costate-alate., Bogor Agricultural University is a campus with high biodiversity. Epiphytic ferns are one of the most abundant plants in terms of numbers and types, but information on their reproductive structures is still limited. This study aims to characterize the reproductive structure of epiphytic ferns that grow in the IPB campus area, Dramaga, Bogor. The research method consisted of a collection of sorus, preserving it with 70% alcohol, observing using a compound microscope connected to an optilab camera, and measuring using the imageRaster v2.1 application. The observed epiphytic ferns varied in the arrangement and location of the sorus and the characteristics of the spores. The sorus was round and line. Most of the sorus were located on the leaf margins. A total of 22 fern species had monolete spore with line laesura, one species had round spore, and one species had tetrahedral-globose spore with triradiate laesura. Spore sizes found were medium, large, and very large. All spores had a P/E ratio value of ≤1.00 with peroblate, oblate, suboblate, round oblate, and round prolate types. The surface of the perispora is very diverse, namely alate-angular, globules, shallow verrucae, verrucate, echinulate, tuberculate, rugate, globules, echinate, laevate, cristate, regulate, colliculate, granulose, and costate-alate.
Keyword: biodiversity, characterization of spores, perispore surface, sorus

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.
Keyword: