R. LEDIFOLIUM (syns Azalea ledifolia and A. liliiflora).—­Ledum-leaved Azalea.  China, 1819.  A perfectly hardy species.  The flowers are large and white, but somewhat flaunting.  It is, however, a desirable species for massing in quantity, beside clumps of the pink and yellow flowered kinds.  Though introduced nearly three-quarters of a century ago, this is by no means a common plant in our gardens.

R. MAXIMUM.—­American Great Laurel.  North America, 1756.  This is a very hardy American species, growing in favoured localities from 10 feet to 15 feet high.  Leaves oblong-lanceolate, slightly ferruginous beneath.  Flowers rose and white, in dense clusters.  There are several handsome varieties that vary to a wide extent in the size and colour of flowers.  R. maximum album bears white flowers.

R. MOLLE (syn Azalea mollis), from Japan (1867), is a dwarf, deciduous species of neat growth, with flame-coloured flowers.  It is very hardy, and a desirable acquisition to any collection of small-growing shrubs.

R. OCCIDENTALE (syn Azalea occidentalis), Western Azalea, is valuable in that the flowers are produced later than those of almost any other species.  These are white, blotched with yellow at the base of the upper petals; and being produced when the leaves are almost fully developed, have a very pleasing effect, particularly as they are borne in great quantity, and show well above the foliage.  This is a Californian species that has been found further west of the Rocky Mountains than any other member of Ihe family.

R. PARVIFOLIUM.—­Baiacul, 1877.  This is a pleasing and interesting species, with small deep-green ovate leaves, and clusters of white flowers, margined with rose.  It is of dwarf and neat growth, and well suited for planting on the rock garden.

R. PONTICUM.—­Pontic Rhododendron, or Rose Bay.  Asia Minor, 1763.  This is the commonest species in cultivation, and although originally a native of the district by the Black or Pontic Sea, is now naturalised in many parts of Europe.  It is the hardiest and least exacting of the large flowered species, and is generally employed as a stock on which to graft the less hardy kinds.  Flowers, in the typical species, pale purplish-violet and spotted.  There is a great number of varieties, including white, pink, scarlet, and double-flowering.

R. PONTICUM AZALEOIDES (syn R. ponticum deciduum), a hybrid between R. ponticum and a hardy Azalea, is a sub-evergreen form, with a compact habit of growth, and bearing loose heads of fragrant lavender-and-white flowers.  It is quite hardy at Kew.

R. RACEMOSUM.—­Central China, 1880.  A neat little species, of dwarf, compact growth, from the Yunnan district of China.  The flowers are pale pink edged with a deeper tint, about an inch across, and borne in terminal and axillary clusters.  It has stood unharmed for several years in southern England, so may be regarded as at least fairly hardy.  Its neat dwarf growth, and flowering as it does when hardly a foot high, renders it a choice subject for the Alpine garden.