n. A genus of shrubs or herbs, of the natural order Saxifrageæ, type of the tribe Hydrangeæ, containing about 33 species, natives of Asia and America, characterized by having the ovary inferior, 4 or 5 valvate petals, 4 or 5 styles, free or connate at base, the fruit a capsule, and the leaves deciduous or persistent.n. [lowercase] A plant of this genus.