The apricot is a species of Prunus, classified with the plum in the subgenus Prunus. The native range is somewhat uncertain due to its extensive pre-historic cultivation. The fruit is a drupe similar to a small peach, 1.5–2.5 cm diameter (larger in some modern cultivars), from yellow to orange, often tinged red on the side most exposed to the sun; its surface can be smooth (botanically described as: glabrous) or with very short hairs (botanically: pubescent). The single seed is enclosed in a hard stony shell, often called a “stone”, with a grainy, smooth texture except for three ridges running down one side.