Bhutan's economy is based on agriculture. The main crops are rice, wheat, maize, and millet. The country is heavily Forested, but the absence of good communications has prevented any effective exploitation. The forests of teak and sal ( Shorea robusta ) along the southern foothills are within easy reach of railheads in India. That rail system provides a way for timber to be dispatched to a ready market. The larger proportion of Bhutan's forests is inaccessible. These forests consist of conifers extending over mountain ranges rising to a height of 3,600 meters and more. Bhutan does have limestone, gypsum, and other valuable mineral deposits that will provide raw material for setting up industries, but the field of hortiCulture is the most significant source of advancement for the country. The Bhutan apple is much favored in India, and the climate is also ideally suited for the cultivation of peaches, plums, and apricots. Some liqueur is manufactured.