The abundant rainfall and the constant heat give rise to exuberant vegetation with a wide range of species. There are almost 12,000 species of plants that have been identified in the archipelago, including more than 8,000 species of flowering plants including Philippines national flower sampaguita (Jasminum sambac), about 3,800 kinds of trees, around 1,000 kinds of ferns, and almost 1000 orchids. The marked topographical variations produce a corresponding variety of vegetation patterns, graded in terms of altitude. The thinly populated regions with all-year-round rainfall are still covered with dense evergreen forest, containing a variety of trees of different heights but with a predominance of Dipterocarpaceae (including a number of trees producing fine woods) and an abundance of lianas and epiphytes (fig-trees, orchids). This forest is less rich and exuberant on sandy soils and inundated land, where the swamp forest consists mainly of palms and raffias. Along the coasts are mangrove swamps and coconut groves. The regions which have a dry season are occupied by deciduous forests which also produce valuable timber, like the molave (Vitex pariflora), acle (Albzzia acle), aranga (Homalium luzoniense) and narra (Pterocarpus indicus).There are also open forests with large number of bamboos and above all savannas of cogonales (Imperata cylindrica), which have made great inroads on the forested regions. Open grasslands occupy one-fourth of the land area and ranging up to 2.4 m in height. Most of the savannas have been man-made, as a result of intense and repeated clearing by itinerant slash-and-burn cultivators. Central Mindanao, for example, is a remarkable mosaic of forest and savanna, with the forest surviving only in strips alongside the rivers and on the hills. In the mountainous parts of Luzon, dense forest has a structure modified by altitude, and found mainly in the Zambales and the Cordillera Oriental. The elevation of the forest in Cordillera Central is above 1000 m, shows a predominance of conifers planted under reforestation schemes, with some indigenous species of pines (Pinus insularis, Pinus merkusii and Pinus kesiya).There are also more than 100 species of palm tree in the Philippines. The most typical includes the fan palm (Licuala spinosa), coconut palm (Cocos nucifera) and nipa palm ( Nypa frutescens) which grows in coastal swamps. The Philippines has a wide variety of flower species. Rafflesia the largest flower species in the world which can be found in Mt Makiling in Laguna, Mt Isarog in Bicol, Mt Apo and Mt Candalaga in Mindanao, Southern Panay and Antique. The Rafflesia mira is the largest among its species with a diameter between 22 cm and 29 cm. Some of the variety of orchids endemic in the country are the lady slipper orchid (Paphiopedilum hennisianum), white or ivory flower with magenta bars (Phalaenopsis lueddemanniana), pearl-white flower (Micropera philippinensis), necklace orchid (Dendrochilum magnum) and waling-waling (Vanda sanderiana).