rubia tinctorum l. (rubiaceae) or madder as one of the living color to dyeing wool

the medicinal part of rubia tinctorum is the dried root. the small yellowishgreen flowers are in loose, leafy, long-peduncled terminal or auxiliary cymes. the margin of the calyx is indistinct, 4- to 5-sectioned and has a tip that is curved inward. there are five stamens and an inferior ovary. the fruit is a black, pea-sized glabrous, smooth drupe containing two seeds. the perennial plant grows to a height of 60 to 100 cm. the pencil thick rhizome creeps widely underground. the stem is quadrangular with backward turning prickles at the edges