The Viola family is a large one, consisting of about 200 species, the greater number being spread over the northern temperate regions, while thirty are found in South America, two in South Africa, and eight in Australia and New Zealand. They are beautiful, woodland plants, and they also inhabit hedge banks, open pastures, and cultivated fields. Most of the species are perennial, and the plants are of dwarf habit. In this country they are nearly all easy to grow in light, rich soil, preferably in half-shady situations, although many of them flourish in the open border. In many of the species the flowers are cleistogamous, the larger petalled flowers appearing first, but producing little or no seed, while later, small petalled fertile flowers are produced which furnish seed. The section to which the Pansy (F. tricolor) belongs is an exception, for in this case all the flowers are fertile. Violas can be propagated by division of the roots, by seeds, runners, or cuttings. About fifty species are in cultivation, the greater number of which are only found in Botanic Gardens.
V. alpina. - This grows at high elevations on the Eastern Alps. It has small, oval-shaped leaves borne on long stalks. The flowers are purple and have a short spur.
V. altaica. - This species is supposed to be one of the parents of the cultivated Pansy; all those with pale-yellow petals with an undulated margin being derived from this plant. It is a native of the Altai Mountains, and has large pale-yellow flowers, with a few dark-purple lines near the base of the petals. It was introduced into cultivation in 1805, and the plants are easily propagated by seeds or cuttings.
V. arenaria. - This is a rare native plant found in Teesdale. It has small leaves and pale-blue flowers. Its native habitat extends into various parts of Europe.
V. biflora. - The twin-flowered Violet is a dainty little plant found on the Alps of Europe, and also in Siberia. It has small, bright-yellow flowers, and must be given a moist position. It was introduced in 1752.
V. blanda. - An early flowering species from North America, with pubescent leaves, and white, small, faintly-scented flowers; the lateral petals are veined with lilac.
V. calcarata. - The alpine Pansy is a lovely plant, forming tufts of foliage, and bearing large violet and purple flowers in the typical plant. There are white, yellow (var. Zoysii), and pale lilac forms in cultivation, it being a most variable plant. It was introduced from the European Alps in 1752.
V. canadensis. - This is a handsome plant, growing nearly one foot high, with white sweetly-scented flowers tinged with violet. It is a native of Canada, and was introduced in 1783. V. Rydbergii is the Colorado form of this species. Both plants require a shady situation.
V. canina (Dog Violet). - This well-known species is a native of Britain and other countries. The flowers are blue, and they have a yellow spur. The species is very variable, one variety having pure white flowers.
V. cenisia. - A lime-loving species from the Alps, with violet flowers and a slender, arching spur. It grows about 6 inches high, and has slightly hairy leaves. 1759.
V. comuta (Horned Viola). - A free-growing species forming dense carpets of foliage, and large, light-purple flowers. It is a valuable spring and summer flowering plant. There is also a pure white-flowered form, as well as other colour varieties, some of which are shown on the coloured plate. It was introduced from the Pyrenees in 1776, and is supposed to be one of the parents of the bedding Violas.
V. cucullata. - This Violet has the margins of the leaves turned up so as to resemble a kind of cup. It is a common North American Violet, and will grow almost anywhere.
The flowers of the type are purple and of good size. There is also a pure white variety. V. septentrionale, with striped, white flowers, is also a form of this species, which has been in cultivation since 1795.
Plate 8. Three Varieties Of Viola Cornuta
V. elatior. - This is a very distinct species growing over one foot high, having a bush habit and erect stems; the flowers are pale blue. It is a native of Europe.
V. gracilis. - A beautiful, dwarf, free-flowering kind from Greece, with large, deep-purple flowers that appear in spring and summer. It is a valuable plant for the rock garden or border. Although introduced in 1817, it has only recently become plentiful in gardens. The variety Valderia (heterophylla) is a charming variety from the Tyrol, and with smaller violet-blue flowers spotted with darker violet and white.
V. hastata is a North American species with hastate leaves and pale, violet-coloured flowers.
V. hederacea. - A charming species of creeping habit, only 2 inches high, with lovely, lilac-blue and white flowers. These are produced freely in summer, and are very attractive. The plant likes a moist position. It is also known as Erpetion reniforme, and is a native of Australia, and is only hardy in very sheltered situations.
V. hirta. - A native and European plant closely allied to V. odorata, but very faintly scented, and with paler flowers.
V. Jooi. - A compact-growing European species with fragrant flowers.
V. lutea. - This is considered to be a form of V. tricolor, and has large, yellow flowers with purple blotches. It is very free in flowering, and has a spreading habit. This species has been used for crossing with the Show Pansy to produce the modern Violas.
V. mirabilis. - This species bears sweetly-scented, pale violet-coloured flowers in April and May.
V. Munbyana - This plant produces a profusion of large, rich-violet flowers through spring and summer. It is a free-growing plant, soon forming a broad carpet of creeping stems. Closely allied to V. lutea. Native of Spain and other places.
V. Nuttallii. - This species grows on the sandy plains of the Missouri in North America; it has pale-yellow flowers.
V. odorata (Sweet Violet). - The delightful fragrance of this species makes it a favourite in every garden. It is a native of this country, and is found over the whole of Europe, extending even into Asia. There are numerous varieties, which have been greatly improved for garden purposes. The flowers range in colour from blue to red, purple, and white. V. odorata pallida-plena, the Neapolitan Violet, has sweet-scented, double flowers of a pale-lavender shade.
V. palmata - A North American species, closely allied to V. cucullata, but its mature leaves are palmately-lobed.
Its native habitat is in low grounds and woods, and it bears bright blue, rarely white, flowers.
V. palustris. - This is a marsh-loving species, with reniform leaves and lilac-coloured or white flowers with short spurs. It is widely spread over the northern temperate regions, including Britain.
V. Patrinii. - This species is also widely distributed from Russia to Japan. It is distinct on account of the leaves having winged petioles. The purple flowers are of medium size.
V. pedata - A beautiful species found growing in dry sandy woods and rocky hills in North America. The leaves are pedately divided into about seven linear divisions, while the large, bright-blue flowers are freely produced. V. p. var. bicolor is a handsome kind, with the two upper petals of a deep violet colour. There is also a pure white form. It was introduced in 1759.
V. pedatifida (syn. V. delphinifolia), - This species is closely allied to V. pedata, but has fewer divisions of the leaves, and smaller, brilliant-blue flowers. It grows on the prairies of Missouri in North America.
V. persicifolia (syn. V. stagnina) is a form of V. canina, but rather taller in habit, with pale-blue or white flowers. It is usually found in boggy ground, and is a native of this country and other parts of Europe. The leaves are rather long and narrow.
V. pinnata (syn. V. dissecta). - This species grows about 6 inches high, and has palmati-partite leaves with toothed segments. It is found in mountain pastures on the Alps of Europe, and is somewhat rare. The violet-coloured flowers are produced in June. The species has been in cultivation since 1752. A form of this species, var. chcerophylloides, with larger and more attractive flowers, is found in Japan.
V. pratensis. - This is similar to V. persicifolia, but is usually found in drier meadows and woods.
V. primulaefolia. - A species inhabiting wet meadows in North America. It has sweet-scented white flowers, the lateral petals being bearded.
V. pubescens. - A free-growing, North American plant, 6 inches to 12 inches high, found in dry woods. It is softly pubescent, with large leaves and yellow flowers; the lower petals are veined with purple. The variety scabriuscula is a form with decumbent stems, and smaller, somewhat scabrous leaves.
V. rostrata. - This is also a North American species found in moist, rocky situations. The large flowers are pale blue and have a slender spur.
V. rothomagensis. - This belongs to the same type as V. cornuta. It has bright-blue flowers, the side petals and lip striped with black. It flowers from April to August, and is a native of France and Belgium.
V. rotundifolia. - At flowering time the leaves of this North American plant are small, but later they develop to a large size, 4 inches in diameter. It is found in shady rocky situations, and bears good-sized pale-blue flowers.
V. sagittata. - Found on hillsides and fields in North America. It has hastate leaves and bright-blue flowers.
V. Sarmentosa. - A creeping species, with stolons and cordate leaves. The flowers are yellow.
V. striata. - A strong-growing, attractive plant, often 12 inches high. The flowers are cream-coloured, the lower petals being veined with purple. It grows in wet meadows in mountainous districts in North America.
V. suavis. - The Russian Violet is closely allied to our native Sweet Violet, but is distinguished by its pale-green leaves and larger, paler flowers. It was introduced from the Caucasus in 1820.
V. sylvestris (Wood Violet). - A well-known native plant with bluish-purple and lilac-coloured flowers, produced on axillary branches from a radical rosette. It is also known as V. sylvatica. There are several forms of this species, such as the varieties Reichenbackiana and Riviniana.
V. tricolor. - (Heartsease; Pansy). - A common very variable annual, found in cultivated fields. The flowers vary from small yellow blooms to large tricolored ones, blue, purple, and yellow. It is one of the parents of the garden Pansy. The variety arvensis has small, yellow flowers.
V. uliginosa. - This European species is similar in habit to the American V. cucullata, but the leaves are flat. The blue-purple flowers have no scent.
V. variegata. - A species from Eastern Asia, with variegated leaves and pale violet-coloured flowers. It blooms in May and June.
The above-mentioned species are merely the commonest of those in cultivation.