The genus Azalea may be divided into three kinds, viz., A. indica and its allied species; A. pontica and its varieties and hybrids; and the American Azaleas. These divisions are easily distinguished by their flowers. Those of the Indian or Chinese Azaleas have all large showy flowers, on short downy footstalks, and they are produced in small clusters of only two or three flowers each, at the extremity of the shoots. The corollas are bell-shaped and deeply cut, nearly to the base, into broad spreading segments. The stamens are ten in number, shorter than the corolla, and of unequal length. The leaves are evergreen, and they are numerous, thickly set and downy. These Azaleas are all very handsome, but the white Indian Azalea (A. indica alba, or A. ledifolia) is particularly so, and very fragrant. The species belonging to this division are mostly natives of China, and require either a greenhouse or some slight protection during winter in England.
The yellow Azalea (A. pontica or Rhododendron flavum) differs from A. indica in being quite hardy; in the flowers being produced in umbels of from eight to twelve, at the ends of the branches, before the leaves; and in the corollas being funnel-shaped instead of campanulate. The tube of the funnel is, however, shorter than the limb, the segments of which are broad and spreading, the upper three being larger and of a darker yellow than the two below. There are usually five stamens, projecting a little beyond the corolla, and curving upwards; the style also curves upwards, and it is crowned by the stigma, which forms a round green head.
The calyx is very small, and both it and the corolla feel clammy to the touch. The flowers are fragrant. The leaves are deciduous, and they are ovate, slightly hairy, and terminate in a mucro or stiff point. There are many varieties of this species, and many hybrids between it and the American kinds, all of which are quite hardy in British gardens.
The principal American Azaleas are A. nudiflora, A. viscosa, A. nitida, and A. speciosa, all of which have the corollas of their flowers funnel-shaped. Of these A. nudiflora is easily known by its stamens, which project a long way beyond the corolla, and by the tube of the corolla being longer than the limb. The plant is deciduous; and the flowers, which are produced in large terminal clusters, and which are not clammy, appear before the leaves. The common English name for this plant in some parts of the country is the American Honeysuckle, and the flowers are of various shades of red, pink, white, and purple. A. calendulacea, which some botanists make a variety of this species, has much larger flowers, and the leaves pubescent on both surfaces, whereas, in A. nudiflora the leaves are nearly smooth and green, with only a slight fringe of hairs round the margin. There are numerous varieties of A. calendulacea, the flowers of which are always either yellow, red, orange, or copper-coloured, and it is supposed to be the parent of the beautiful Ghent Azaleas. A. viscosa has the tube of the corolla equal in length to the limb, and rather short stamens; the flowers of this species are clammy. A. hispidum, which is generally considered a variety of A. viscosa, is still more clammy, and the tube of the corolla is wider and shorter; other probable varieties are A. nitida, which has shining leaves, and A. glauca, which has glaucous ones, as in both kinds the flowers are very clammy. A. speciosa has large flowers and leaves tapering at both ends. All the species of Azalea have five stamens, but some of the varieties have ten.
Rhodora canadensis is a little American shrub with pink flowers, which appear before the leaves, and the corolla of which is bilabiate, the upper lip being the broadest, and cut into two or three teeth, and the lower only once cut. There are ten stamens, and the capsule is five-celled and five-valved. The leaves are deciduous, and slightly pubescent beneath; and the flowers are produced in small terminal clusters. This plant, as well as all the Azaleas above described, are now included by some botanists in the genus Rhododendron.
The genus Kalmia also belongs to this tribe. The flowers of this well known shrub are very curiously constructed. The corolla is salver-shaped, that is, nearly flat, and on the under side of the limb are ten protuberances, producing as many hollows on the upper side, in which lie half-buried the ten stamens. This singular construction gives the corolla that wrinkled appearance which has procured for the plant its American name of Calico flower; while, from the shape of the leaves, it is also frequently called the Mountain laurel; it is also called Sheep laurel from its being considered poisonous to those animals when they feed on it. There are several species, which differ from each other principally in the shape of their leaves and the size of their flowers.
Menziesia is a genus containing only three species, of which M. pilosa (fig. 60) may be taken as an example. The flowers are small and bell-shaped, and the anthers (a) are without any awns or bristles; there are eight stamens, and the curious manner in which they are crowded round the style is shown at b. The capsule is four-celled.
