Citrus is an important group of trees and shrubs of the genus Citrus in the family Rutaceae. They include grapefruit, kumquat, lemon, lime, orange, tangerine, and ugli. Native to subtropical regions, they are widely cultivated wherever there is plenty of sun and moisture. The stems are usually thorny, the leaves bright green, shiny and pointed. The flowers are usually white, waxy, and fragrant. The fruit is usually ovoid with a thick, aromatic rind. The inside of the fruit is pulpy and juicy and is divided into segments that contain the seeds. Most citrus fruits contain significant amounts of vitamin C.