epiphytal, growing on the branches of other trees, but not deriving their sustenance from them. The varieties grown in gardens are mostly grafted on the Pontic species (R. ponticum) and the Virginian R. calawbiense. The common Pontic variety is excellent for game-covert, from its hardiness, the shelter it affords, and the fact that hares and rabbits rarely eat it. Variety of colour has been infused by crossing or hybridizing the species first named, or their derivatives, with some of the more gorgeously coloured Himalayan-American varieties. In many instances this has been done without sacrifice of hardihood.
Some of the finest hybrids for the open air, especially in favoured spots, are altaclerense (scarlet); Harrisi (rosy crimson); Kewense (rose); Luscombei (rose-pink); Manglesi (white); nobleanum (crimson), one of the first to flower after Christmas; praecox (rose-purple); and Shilsoni (crimson). There are almost countless colour variations of these, but one of the most exquisite of late years is that known as Pink Pearl, with large clear rosy-pink blossoms of great purity. What are termed greenhouse rhododendrons are derivatives from certain Malayan and Javanese species, and are consequently much more tender. They are characterized by the possession of a cylindrical (not funnel-shaped) flower-tube and other marks of distinction. The foliage of rhododendrons contains much tannin, and has been used medicinally. Whether the honey mentioned by Xenophon as poisonous was really derived from plants of this genus as alleged is still an open question.
Cultivation.—The hardy evergreen kinds are readily propagated by seed, by layers, and by grafting. Grafting is resorted to only for the propagation of the rarer and more tender kinds. Loamy soil containing a large quantity of peat or vegetable humus is essential, the roots of all the species investigated being associated with a fungus partner (mycorhiza). An excess of lime or chalk in the soil proves fatal to rhododendrons and their allies sooner or later—a fact overlooked by many amateurs. The hardy deciduous kinds are valuable for forcing, and withstand cold-storage treatment well. The tender Malayan and Javanese species thrive in warm greenhouse temperature, but are difficult to cultivate where the water is very alkaline.
RHODONITE, a member of the pyroxene group of minerals,
consisting of manganese metasilicate, MnSiO3, and crystallizing
in the anorthic system. It commonly occurs as cleanable to
compact masses with a rose-red colour; hence the name, from
the Greek ῥόδον (a rose). Crystals often have a thick tabular
habit; there are perfect cleavages parallel to the prism faces
with an angle of 87° 3112′. The hardness is 512–612, and the
specific gravity 3·4–3·68. The manganese is often partly
replaced by iron and calcium, which may sometimes be present
in considerable amounts; a greyish-brown variety containing
as much as 20% of calcium oxide is called “bustamite”;
“fowlerite” is a zinciferous variety containing 7% of zinc
oxide. Rhodonite is a mineral liable to alteration, with the
formation of manganese carbonate, hydrous silicate or oxides.
The compact material, which is cut and polished for ornamental
purposes, is often marked in a striking manner by veins and
patches of these black alteration products. At Syedelnikova,
near Ekaterinburg in the Urals, compact material of a good
colour occurs in a clay-slate and is extensively quarried: boulders
of similar material found at Cummington in Massachusetts
(“cummingtonite”) have also been worked as an ornamental
stone. In the iron and manganese mines at Pajsberg near
Filipstadt and Långban in Vermland, Sweden, small brilliant and
translucent crystals (“pajsbergite”) and cleavage masses
occur. Fowlerite occurs as large, rough crystals, somewhat
resembling pink felspar, with franklinite and zinc ores in granular
limestone at Franklin Furnace in New Jersey.
RHOECUS, a Samian sculptor of the 6th century B.C. He and
his son Theodorus were especially noted for their work in bronze.
Herodotus says that Rhoecus built the temple of Hera at Samos.
In the temple of Artemis at Ephesus was a marble figure of
night by Rhoecus. His name has been found on a fragment of a
vase which he dedicated to Aphrodite at Naucratis. His sons
Theodorus and Telecles made a statue of the Pythian Apollo
for the Samians.
RHONDDA (formerly Ystradyfodwg), an urban district and
parliamentary division of Glamorganshire, South Wales. It
is 12 m. long by about 434 m. across at its widest part, and
comprises two main valleys, named after their respective rivers,
Rhondda Fawr (912 m.) and Rhondda Fach, or the lesser (612 m.),
running S.E. and S.W. respectively till their junction at Porth,
and thence the single valley for upwards of a mile farther down
the boundary of the Pontypridd urban district at Trehafod.
The valleys are narrow and tortuous, and their lateral boundaries
are formed by steep hills varying in height from about 560 ft.
on either side of Trehafod to 1340 ft. on the N.E. of:Maerdy in
the lesser Rhondda and 1742 ft. on the S.W. of Treherbert in the
main valley, while the mountains at the upper end of the latter
valley culminate in Carn Moesen (1950 ft.). The two valleys are
separated by the steep ridge of Cefn-rhondda, which ranges from
600 ft. high above Porth to 1690 ft. near the upper end of the
district. There are a few tributary valleys of which Cwmparc,
Clydach Vale and Cymmer are the chief. Though the urban
district measures 23,884 acres, the area built upon is generally
a narrow strip on either side of each river except at Treorky
and Ton, where the valley of the Rhondda Fawr opens out a
little. In 1877 the ancient parish of Ystradyfodwg (with the
omission of the township of Rhigos, which lies beyond the
mountains to the north) was formed into an urban district
bearing the parish name, the area having previously been part
of a rural district under the Pontypridd rural sanitary authority.
In October 1879, portions of the parishes of Llanwonno and
Llantrisant, comprising over 5000 acres, were added to the urban
area, the whole being consolidated in 1894 into one civil parish.
In 1897, the name of the urban district was changed into
Rhondda. The Taff Vale railway runs up each of the two
valleys from a junction at Porth (16 m. N.W. of Cardiff), and has
five stations in the main valley and four in the lesser one. From
Porth it runs to Pontypridd, whence there is communication
with Cardiff, Barry and Newport. The Rhondda and Swansea
Bay railway (authorized in 1882, opened in 1890, and now
worked by the Great Western) connects the upper end of the
main valley, where it has a station, Blaen-rhondda, with Port
Talbot, Neath and Swansea (31 m. distant) by means of a line
which has a tunnel 3443 yds. long.
The district occupies almost the centre of the eastern division of the South Wales coal-field, and its coal, upon which the inhabitants are almost entirely dependent, is unsurpassed for its steam-raising properties. In common with other East Glamorgan coal it became commercially known as Cardiff coal from the fact that Cardiff was at first its only port of shipment. The development of the Rhondda coal-field was later in date than those of Aberdare and Merthyr, and it received its chief impetus from the American Civil War. Thus the population of the parish (excluding Rhigos), which was 576 in 1811, 951 in 1851 and 3035 in 1861, increased to 16,914 in 1871. When the boundaries of the district were extended in 1879 the population of the enlarged area was calculated by the registrar-general to be 23,950 in 1871, but it reached 55,632 in 1881, and 113,735 in 1901, showing an increase of 104% in the previous twenty years. In 1901, 35·4% of the population of three years of age and upwards spoke English only, 11·4% spoke Welsh only, the remainder being bilingual.
Ecclesiastically the parish of Ystradyfodwg was an ancient chapelry dependent on Llantrisant. The old parish church at Ton Pentre (in substitution for which a new church was built in 1893–94) served the whole parish till past the middle of the 19th century. Between 1879 and 1900 the ancient-parish (excluding Rhigos) was divided into seven ecclesiastical parishes, the six new ones being Llwyn-y-pia (1879), Tylorstown (1887), Ynyshir (1887), Treherbert (1893), Cwmparc (1898) and Ferndale (1900). The additional area brought into the urban district in 1879 comprises two other ecclesiastical parishes, Cymmer and Porth (1894), and Dinas and Penygraig (1901). These nine parishes, comprised in the urban district, have twenty churches and eighteen mission-rooms, with accommodation for about 12,000 persons. This area, together with Pontypridd, Glyntaff and Llanwonno, form the rural deanery of Rhondda in the archdeaconry and diocese of Llandaff. There wer! at the end of 1905 over one hundred and fifty nonconformism chapels and mission rooms, with accommodation for over 85,000 persons, of which provision nearly two-thirds was in chapels with Welsh services. There is a Roman Catholic church at Tonypandy. The public buildings include the council house and offices of the district council, erected in 1883–84 for the local board at Pentre,
libraries and workmen's institutes at Ystrad (1895), and Cymmer