Hydrangea Linn., Sp. P1. 390. 1753. Gen. Pl. ed. 5:189. 1754; C.B. Clarke in Hook. f., Fl. Brit. Ind. 2:403. 1878; Brandis, Ind. Trees, 296.1911; L.H.Bailey, Stand. Cyclop. Hort. 3:1619. 1915; Kirk, Brit.Gard.Fl. 230. 1927; Hutch., Gen. Flow. Pl. 2:21.1968.
Stem softly woody with broad pith. Leaves opposite, decussate, serrate, rarely entire, sometimes deeply lobed, deciduous, petiolate. Flowers in terminal paniculate cymes or corymbs, inner central ones regular, bisexual, a few or majority of the outer ones sometimes sterile, long pedicelled. In sterile flowers sepals 4-5, petaloid, enlarged and distinctly veined; petals 4-5, rudimentary or missing. Fertile flowers perfect, regular; sepals 5-4, imbricate; petals 5-4, valvate; stamens 8-10, anthers short; ovary inferior, 2-5-locular, ovules numerous on T-shaped, introflexed parietal placentas; styles 2-5, short, free or united at the base, stigmas terminal. Fruit a 2-5-locular, membranous capsule opening at the top between the styles. Seeds many, minute; testa membranous, reticulate.
A genus of about 80 species, mostly found in the Himalayas, China, Upper Burma, Java, Japan, E.N. & W.S. America. Majority of the plants are beauti¬ful and ornamental. Represented in W. Pakistan by I cultivated species.