See Chapters 5, 9., 18., and 26., also the chapter on modern shrubs. The most popular species is hortensis (syn. hortensia), but it is often represented in gardens by its varieties, such as Avalanche, Bouquet Rose, Dentelle, Mariesii, Innocence, Madame Mouilliêre, La Lorraine, Otaksa, rosea, Thomas Hogg, variegata and Veitchii. Mariesii has very large pink or reddish mauve sterile flowers and blossoms freely in a small state; the newer Veitchii resembles it in form, but is white. Otaksa is pink and Thos. Hogg white; variegata has green and white foliage. The species has nominally pale pink flowers, but it is well known that in certain soils they become blue, and the change of colour can be induced artificially by watering with a solution of alum, 1oz. to a gallon of water. Although the species is not perfectly hardy it sometimes lives for years outdoors in mild districts. There is one at Shanklin which has carried 6oo heads of blue flowers. It is, of course, grown largely in pots. Paniculata grandiflora (syn. p. hortensis) is a very popular plant with white flowers in autumn; it is hardy. Quercifolia is sometimes grown against walls in mild districts, and the same may be said of petiolaris, which has ivy-like leaves and white flowers in spring. Ordinary soil.