Two main species are found in Iran: common (ʿadas-e maʿmūlī, Lens culinaris) and oriental (ʿadas-e ābī, Lens orientalis). The common lentil grows wild in northwest, east, south and southeast Iran, while the oriental lentil grows around Tehran to the north, west, south and southeast. Used extensively in Persian cuisine, lentils are a major source of protein for the poor. Only the large gray variety, known as French lentils or lentille large blonde, is used. Among the most popular dishes employing lentils is ʿadas-polow: Rice and lentils are cooked separately, then mixed together for the final steaming process, and usually served with chicken or lamb. The dark specks of lentils in the white rice add color as well as flavor; sometimes toasted slivered almonds are sprinkled on top. A less elegant variety mixes tiny meatballs with the rice. Because lentils are inexpensive, ʿadas-polow is considered a family rather than a company dish. Lentils are also used in different kinds of soups, the best known of which are āš-e rešta and āš-e ǰow: Lentils are mixed with other dried legumes, onions, rice, barley, green herbs, and spices to make a thick, filling soup which, served with bread, is a complete meal. Sometimes these soups have a small amount of meat added, usually lamb shank. A less well known variety is āš-e ʿadas, a variation on the same theme, but with a heavier concentration of lentils and a smaller amount of chick peas and beans. The aroma of ʿadasī, frequently sold in stalls on street corners, can permeate an entire block: The lentils are boiled until tender, onions are added with salt and pepper, and the dish is simmered until most of the liquid has been absorbed and the lentils have a thick, almost soupy consistency. A small amount of butter is sometimes added to enhance the flavor.