Judul: Fern Spores Characterization in  Mount Tajam and Mount Lumut, Belitung
Abstrak: Belitung memiliki wilayah yang penting untuk disorot berupa hutan kerangas, yaitu ekosistem dengan media tanah yang miskin unsur hara. Salah satu keragaman flora yang dapat ditemukan di ekosistem ini adalah tumbuhan paku. Beberapa jenis tumbuhan paku memiliki ciri morfologi vegetatif yang mirip sehingga sulit diidentifikasi secara langsung. Oleh karena itu, ciri struktur reproduksi dibutuhkan untuk memantapkan identifikasinya. Penelitian ini bertujuan mendeskripsi ciri spora tumbuhan paku di Gunung Tajam dan Gunung Lumut, Belitung. Karakter yang diamati meliputi bentuk spora, ukuran spora, tipe laesura, dan tipe permukaan perispora. Spora diamati dengan mikroskop majemuk Olympus CX23 dan didokumentasi dengan kamera OptiLab. Spora diukur menggunakan perangkat lunak Image Raster. Data disusun dalam bentuk gambar, tabel karakter spora, dan kunci paralel. Hasil pengamatan menyajikan ciri spora dari 22 jenis tumbuhan paku yang diperoleh dari koleksi herbarium yang telah diidentifikasi. Tipe spora monolete dengan laesura garis ditemukan pada 11 jenis yang bervariasi pada bentuknya yaitu bulat dan lonjong. Tipe spora trilete dengan laesura triradiate ditemukan pada 11 jenis dengan bentuk yang bervariasi yaitu tetrahedral-bundar, bulat, dan berlobus. Tipe permukaan perispora sangat bervariasi antarmarga dan jenisnya. Hasil pengukuran spora berdasarkan rasio P/E memiliki nilai <1,00. Tipe ukuran spora yang ditemukan yaitu medium, besar, dan gigantik., Belitung has a highlighted area namely heath forest, which is an ecosystem with nutrient-poor soil media. One specific biodiversity of flora in this ecosystem is pteridophytes. Some species of pteridophytes have similar vegetative morphological features that are difficult to identify directly. Therefore, the characteristics of the reproductive structure are needed to strengthen its identification. This study aimed to identify the pteridophyte spore’s character from Mount Tajam and Mount Lumut Belitung. The observed spore characters are spore shape and size, laesure type, and perispore ornamentation type. Spores were observed using an Olympus CX23 compound microscope and documented using an OptiLab camera. Spore were measured using Image Raster software. Data is arranged in the form of figure, spore character table, and parallel keys. The observations present the spore characters of 22 species of pteridophytes obtained from the herbarium collections that have been identified. Eleven species have monolete spore types with linear laesure that vary in shape, sphere and ellipse. The other 11 species have trilete spore type with triradiate laesure having various shapes, tetrahedral-globose, sphere, and lobed. The surface type of perispores varies greatly between genera and species. The results of the spore measurement based on the P/E ratio had a value of <1.00. The spore sizes found are medium, large, and gigantic.
Keyword: identification, laesure, ornamentation, perispore, pteridophyta

Judul: Characterization of The Reproductive Structure of Fern in Heath Forest of Mount Agung and Tebat Rasau Ibu, Belitung
Abstrak: Hutan kerangas merupakan hutan dengan vegetasi yang tumbuh pada tanah kaya pasir kuarsa, miskin hara, dan memiliki pH rendah. Hutan kerangas mendominasi sebagian ekosistem hutan di Belitung. Jenis vegetasi yang dapat tumbuh di hutan kerangas salah satunya tumbuhan paku. Penelitian ini bertujuan mengkarakterisasi struktur reproduksi tumbuhan paku yang tumbuh di hutan kerangas Gunung Agung dan Tebat Rasau Ibu, Belitung. Struktur reproduksi diamati dari daun fertil tumbuhan paku dengan menggunakan mikroskop stereo dan mikroskop majemuk yang dihubungkan dengan kamera optilab. Data disajikan dalam bentuk gambar, tabel dan kunci identifikasi, kemudian dianalisis secara deskriptif. Tumbuhan paku yang diamati bervariasi pada susunan dan letak sporangia yaitu sporangia dalam strobilus, segmen seperti jari di tepi daun, sorophore, dan sorus. Sorus berbentuk garis, bulat, dan tabung. Sebagian besar sorus terletak pada tepi daun dan di sekitar tulang daun lateral. Spora dari 12 jenis tumbuhan paku memiliki bentuk dasar elips dengan laesura garis, satu jenis bentuk bulat dan tujuh jenis berbentuk tetrahedral-globose dengan laesura triradiate. Ukuran spora yang dijumpai yaitu medium, besar, dan gigantik. Semua spora memiliki nilai rasio P/E <1,00 dengan tipe oblate, suboblate, dan peroblate. Permukaan perispora sangat beragam yaitu echinulate, cristate, plain/laevate, papillate, echinate, alate, reticulate, verrucate, granulate, globules, tuberculate, dan ridges., The heath forest is a forest with vegetation that grows on soils rich in quartz sand, deficient in nutrients, and have a low pH. The heath forest dominates some of the forest ecosystems in Belitung. One of the types of vegetation that can grow in the heath forest is pteridophytes. This study aimed to characterize the reproductive structure of pteridophytes growing in the heath forests of Mount Agung and Tebat Rasau Ibu, Belitung. Reproductive structures were observed from the fertile leaves of pteridophytes using a stereo microscope and a compound microscope connected to an optilab camera. The data obtained are presented in the form of figures, tables, and identification keys, then analyzed descriptively. The pteridophytes observed varied in the arrangement and location of the sporangia, namely sporangia in the strobilus, finger-like segments on the leaf margins, sorophore, and sorus. Sori are lines, round or tubular in shape. Most sori are located on the leaf margins and around the lateral veins. Spore of 12 species have an ellipsoid spore with linear aperture, one species has a spheroidal spore, and seven species have tetrahedral-globose spore with triradiate aperture. The size of the spores found is medium, large, and gigantic sizes. All spores had P/E ratio values <1,00, with oblate, suboblate, and peroblate spore types. The perispore surface is very diverse: echinulate, cristate, plain/laevate, papillate, echinate, alate, reticulate, verrucate, granulate, globules, tuberculate, and ridges.
Keyword: heath forest, perispore surface, pteridophytes, spore morphology

Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
Keyword: