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5H.5 R H O 
irom all parts ot the trunk. The bark is 
slender, of a brown colour, and, when young, 
is smooth, and adheres very closely lo the 
wood ; but when old, appears quite cracked, 
ana is easily detached irom it. Under this 
ba:k is a skin as thick as parchment, red, and 
adhering closely to the wood, from which it 
cannot be d.tached till the tree is felled and 
<hy. ] he wood is hard, compact, heavy, of 
a deep red, w ith a very tine grain. The pith 
or heart of the wood being cut into small 
pieces, and boiled in water, imparts a very 
beautiful red to the liquid, which communi- 
cates the same colour to wool and linen. 
The great weight and hardness of the wood 
prevent it from being generally used. From 
the fruit o! this tree, which, when ripe, is of a 
violet-colour, and resembles some grapes in 
taste, is prepared an agreeable liquor, much 
esteemed by the inhabitants of the Caribbee 
islands. 
W bite mangle; another variety, so termed 
from the colour of its wood, grows, like the 
two former, upon the banks of rivers, but is 
seldom found near the sea. The bark is 
grey; the wood, as we have said, white, and 
wiien green, supple; but dries as soon as cut 
down, and becomes very light and brittle. 
1 his species is generally called rope-man- 
grv e, irom the use to which the bark is 
applied by the inhabitants of the West In- 
dies. This bark, which, from the great 
abundance of sap, is easily detached when 
given irom the wood, is beaten or bruised 
betwixt two stones, until the hard and woody 
part is totally separated from that which i's 
si.it and tender. T his last, which is the true 
cortical substance, is twisted into ropes of all 
sizes, which are exceedingly strong, and not 
apt to rot in the water. 
RIIODIOLA, rose-zvort, a genus of the 
•ctandria order, in the dioecia class of plants, 
and in the natural method ranking under the 
13th order, succulents*. The male calyx is 
quadripartite, the corolla tetrapetalous. 'The 
female calyx is quadripartite, and there is no 
torulla; the nectaria are four; the pistils 
four ; and there are four polyspermous cap- 
sules. i here are two species, the rosea and 
tiie biternata; the first grows naturally in 
the clefts ot the rocks and rugged mountains 
ef Wales, Yorkshire, and Westmorland. It 
has a very thick fleshy root, which when cut 
or bruised sends out an odour like roses. It 
has thick succulent stalks, like those of or- 
pine, about nine inches long, with thick suc- 
culent leaves indented at the top. The stalk 
is terminated by a cluster of yellowish herba- 
ceous flowers, which have an agreeable scent, 
but are of short continuance. The second 
sort is a native of Cochin China. Both spe- 
cies are easily propagated by parting their 
roots, and require a shady situation and dry 
undunged soil. The fragrance of the first 
species, however, is greatly diminished by 
cultivation. 
RHODODEN D ft U M, dwarf rose-bay, 
a genus of the monogynia order, in the de- 
candria class of plants, and in the natural 
method ranking under the 18th order, In- 
comes. The calyx is quinquepartite ; the 
corolla funnel-shaped ; the stamina declining; 
the capsule quinquelocular. There are nine 
species ; the most remarkable of which are, 
1. The hirsutum, with naked hairy leaves, 
grows naturally onihe A ! p> and several moun- 
tains of Italy. It is a low shrub, which sel- 
dom rises two feet high, sending out many 
ligneous branches covered with a light-brown 
bark, and oval spear-shaped leaves, sitting 
pretty close to t ire branches. They are en- 
tire, having a great number of line iron-co- 
loured hairs on their edges anti underside. 
The flowers are produced in bunches at the 
end ot the branches in May, having one fun- 
nel-shaped petal cut into Jive obtuse seg- 
ments, and of a pale-red colour. 
2. The ferrugineum, with smooth leaves, 
hairy on their underside, is a nance of the 
Alps and Apennines. It rises with a shrubby 
stalk near three feet high, sending out many 
irregular branches covered with a purplish 
bark, and smooth spear-shaped entire leaves, 
whose borders are retiexed backward ; the 
upper side is of a light lucid green, their un- 
der side of an iron-colour. The flowers are 
produced at the ends of the branches, are 
tunnel-shaped, cut into live segments, and of 
a pale rose-colour. These plants are propa- 
gated by seeds ; but being natives of barren 
rocky soils and cold situations, they do not 
thrive in gardens, and for want of their usual 
covering of snow in the winter, are often 
killed by frost in this country. 
3. The chaniaicislus, or ciliated-leaved 
dwarf rose-bav, is a low deciduous shrub, 
native of mount Baldus, and near Sallzburg, 
in Germany. It grows to the height of about 
a yard ; the branches are numerous, produced 
irregularly, and covered with a purplish bark. 
I he leaves are oval, spear-shaped, small, and 
i‘- flic under surface of the colour of iron. 
The flowers are produced at the end of the 
branches in bunches, are of a wheel-shaped 
figure, pretty large, of a line crimson colour, 
and handsome appearance. They appear in 
June. 
4. The dauricum, or Daurian dwarf rose- 
bay, is a low deciduous shrub, and native of 
Dauria. Its branches are numerous, and 
covered with a brownish bark. The flowers 
are wheel-shaped, large, and of a beautiful 
rose-colour: they appear in May, and are 
succeeded by oval capsules full of seeds, which 
in England do not always ripen. 
5. r i he maximum, or American mountain 
laurel, is an evergreen shrub, and native of 
Virginia, where it grows naturally on the 
highest piountains, and on the edges of cliffs, 
precipices, &c. where it reaches the size of a 
moderate tree, though with us it seldom rises 
higher than six feet. The flowers continue 
by succession sometimes more than two 
months, and are succeeded by oval capsules 
full of seeds. 
6. T he ponticum, or pontic dwarf rose- 
hay, is an evergreen shrub, native of the 
East, and of most shady places near Gibral- 
tar. It grows to the height of four or live 
feet. The leaves are spear-shaped, glossy 
on both sides, acute; and placed on short 
foot-stalks on the branches: the flowers, 
which are produced in clusters, are bell- 
shaped, and of a line purple colour. They 
appear in July, and are succeeded by oval 
capsules containing seeds, which in England 
seldom attain to maturity. 
In Siberia, a species of this plant is used 
with great success in gouty and rheumatic 
affections ; and the inhabitants of Siberia call 
Ibis shrub chei or tea, from their drinking in 
common a weak infusion of it, as we do the 
plant oi that name. This practice 
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shows that the plant, used in small quantities^ 
must be innocent. 
RIlOGOftA, a genus of the decandria 
monogynia class and order. The calyx is- 
live-toothed; petals three, unequal; stamina 
declined ; capsules live-ceiled. * 1 here is one 
species, a shrub of Newfoundland. 
ftliOPALA, or ft up ala, a genus of the 
monogynia order, in the tetrandria class of 
plants, and in the natural method ranking 
w ith those that are doubtful. "There is no 
calyx ; the petals are four, oblong, obtuse, 
and narrowing at the base; the stamina are 
four, inserted in the corolla, and have large 
ant b era ; the seecl-vessel unilocular, and con- 
tains one seed. 'There are only two species. 
The montana is a shrubby plant growing hi 
Guiana, and remarkable for the great num- 
ber of branches sent off from its trunk in 
every direction, and for the fetid smell of the 
wood and bark ol this plant. The other is a. 
native of Cayenne. 
RHOMBOIDEb. See Geometry. 
RHOMBUS. See Geometry. 
RHUBARB. See Rheum, and Phar- 
macy. 
RHUMB, in navigation, a vertical circle 
of any given place, or the intersection of such „ 
a circle with the horizon ; in which last sense ’ 
rhumb is the same with a point of the com- 
pass. 
Rhumb-line, is also used for the linei 
which a ship describes when sailing in the- 
same collateral point of the compass, or i 
oblique to the meridians. See Naviga- 
tion. 
RHUS, sumach, a genus of the trUynia j 
order, in the penlandria class of plants^ and 
m the natural method ranking under the 43d 
order, dumossc. liie calyx is quinquepar- 
tite ; the petals five ; the berry monosper- j 
mous. I here are 34 species, of which the" 
most remarkable are, 
1. lhe coriaria, or elm-leaved sumach 
grows naturally in Italy, Spain, Turkey Sy- 
ria, and Palestine. The branches of this* tree 
are used instead of oak-bark for tanning of 
leathei ; and it is said that the Turkey leather 
is all tanned with this shrub. It has a lie- i 
neous stalk, which divides at bottom into ; 
many irregular branches, rising to the height 
of eight or ten feet ; the bark is hairy, of a 
heibaceous biown colour \ the leaves are 
winged, composed of seven or eight pair of 
lobes, terminated by an odd one, bluntly 
sawed on their edges, hairy on their under : 
side, ot a yellowish-green colour, and placed 
alternately on the biancnes; the flowers °tow 
in loose panicles on the end of the branches 
which are of a whitish herbaceous colour 
each panicle being composed of several spikes 
of flowers sitting close to the footstalks. The 
leaves and seeds of this sort are used in me- i 
dicine, and are esteemed very reslrin<rent 
and styptic. ° 
2. 'I'he typhinum, Virginian sumach, or 
vinegar-plant, grows naturally in almost every 
part of North America. This has a woody 
stem, with many irregular branches, which 
are generally crooked and deformed. The 
young branches are covered with a soft vel- 
vet-like down, resembling greatly that of a 
young stag’s horn, both in colour and texture, 
whence the common people have given it the ^ 
appellation of stag’s horn; the leaves are ; 
winged, composed of six or seven pair of oh- 
