This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Shrubs, or some Asiatic species small trees, with opposite simple petioled leaves and terminal corymbose flowers. Stipules none. Exterior flowers of the corymb often apetalous, slender-pedicelled, sterile, but with enlarged and very conspicuous calyx-lobes, or sometimes the whole corymb changed to these sterile flowers; fertile flowers small. Calyx-tube (hy-panthium) hemispheric or obconic, adnate to the ovary, 4-5-lobed. Petals 4 or 5, valvate. Stamens 8 or 10, inserted on the disk. Filaments filiform. Ovary 2-4-celled; styles 2-4, distinct, or united at the base; ovules . Capsule membranous, usually 2-celled, ribbed, many-seeded, dehiscent at the bases of the styles. [Greek, water-vessel, from the shape of the capsule.]
About 35 species, natives of eastern North America, eastern Asia and the Himalayas, and South America. Besides the following, 2 or 3 others occur in the southeastern States. Type species: Hydrangea arborescens L.
Leaves glabrous or somewhat pubescent beneath.
Leaves tomentose beneath.
H. arborescens L. Sp. Pl. 397. 1753. Hydrangea vulgaris Michx. Fl. Bor. Am.
1: 268. 1803. Hydrangea arborescens kanawhana Millsp. Bull. W. Va. Agric. Exp. Sta.
2: 363. 1891.
A shrub, 4°-10° high, the young twigs pubescent or glabrate. Petioles slender, 1'-4' long; leaves ovate, thin, 3'-6' long, acute or often acuminate at the apex, rounded, cordate or rarely broadly cuneate at the base, sharply dentate, green both sides, or pale beneath, glabrous above, sometimes pubescent beneath; cymes 2'-5' broad; marginal sterile flowers usually few or none, but sometimes numerous, or forming the entire inflorescence, capsule wider than long.
On rocky stream or river banks, southern New York and New Jersey, very abundant in the valley of the Delaware, to Iowa, south to Florida, Louisiana and Missouri. Ascends to 4200 ft. in North Carolina. June-July, sometimes blooming again in Sept. Seven-barks. Hills-of-snow.
2. Hydrangea cinŔrea Small. Ashy Hydrangea. Fie. 2188.
Hydrangea cinerea Small, Bull. Torr. Club 25: 148. 1898.
A shrub 6°-8° high, the twigs finely pubescent or glabrate. Leaves slender-petioled, ovate, rounded or cordate at the base, acute or acuminate at the apex, 3'-6' long, slightly thicker than those of the preceding species, green and nearly glabrous above, tomentose beneath; marginal flowers, or at least some of them, sterile and conspicuous; capsule longer than wide.
Missouri to Tennessee and North Carolina, south to Georgia. Snowy-hydrangea. June-July. Confused in our first edition with Hydrangea radiata Walt., of the southeastern states which has leaves silvery-white beneath.