BUCKTHORN, known botanically as Rhamnus catharticus (family Rhamnaceae), a much-branched shrub reaching Loft. in height, with a blackish bark, spinous branchlets, and ovate, sharp ly-serrated leaves, 1 to tin. long, arranged several together at the ends of the shoots. The small green flowers are regular and have the parts in fours; male and female flowers are borne on different plants. The fruit is succulent, black and globose, and contains four stones. The plant is a native of England, occurring in woods and thickets chiefly on chalk; it is rare in Ireland and not wild in Scotland. It is native in Europe, north Africa and north Asia, and naturalized in parts of eastern North America. The fruit has purgative properties ; the bark yields a yellow dye.
An allied species, Rhamnus Frangula, is also common in Eng land, and is known as berry-bearing or black alder. It is dis tinguished from buckthorn by the absence of spiny branchlets, its non–serrated leaves, and bisexual flowers with parts in fives.
Sea-buckthorn is Hippophae rhamnoides (family Eleagnaceae), a willow-like shrub, 1 to 8f t. in height, with narrow leaves silvery on the underside, and globose orange-yellow fruits one-third of an inch in diameter. It occurs on sandy seashores from York to Kent and Sussex, but is not common.
In the United States there are 12 or more native species of buckthorn, most numerous on the Pacific coast, 8 occurring in California, one of which, R. Purshiana yields the medicinal Cascara sagrada (q.v.).