Rhododendron 
2. [/. <.] Any one of the many species of the 
above genus, belonging to the section Rhododen- 
dron; the rose-bay. The rhododendrons are hand- 
some shrubs, much cultivated for their evergreen leathery 
leaves and profusion of beautifully formed and colored 
flowers. The ordinary species of American outdoor plan- 
tations is /{. Catau'bifiise, the Catawha or Carolina rhodo- 
dendron, hybridized with the more tender exotics R. Pan- 
ticuin and R. arbareum. The Catawba species grows from 
3 to 8, rarely 20, feet high, has oval or oblong leaves and 
broadly bell-shaped lilac-purple or (in culture) variously 
colored flowers. It is native in the Alleghanies from Vir- 
ginia southward. It has also been largely cultivated in 
Europe, and there are hundreds of varieties. The great 
rhododendron (or laurelX R. maximum, abounds in the Al- 
Flowering Branch of the Great Laurel ( Rhododendron maximum). 
leghanies, and is found as far north as Maine and Canada. 
It is commonly taller than R. Catawbiense, with narrower 
leaves, and flowers pink or nearly white with a greenish 
throat. It is a fine species, but much less cultivated than 
the last ; it affords some hybrids. The Californian rhodo- 
dendron, R. Caltfomicum, resembles the Catawba rhodo- 
dendron, but has more showy flowers. It deserves culti- 
vation, and has proved hardy in England. The Pontic rho- 
dodendron, R. Ponticmn, is the most common species of 
European gardens, hardy only as a low shrub in the north- 
ern United States. R. arboreum, the tree rhododendron, 
is a fine Himalayan species, 25 feet high, with the leaves 
silvery-white beneath, and the flowers scarlet varying to 
white. The Lapland rhododendron, R. Lapponieum, is a 
dwarf arctic and alpine species of both hemispheres, grow- 
ing prostrate in broad tufts. The Siberian or Dahurian 
rhododendron, R. Dauricum, a dwarf species, somewhat 
cultivated, bears its bright rose-purple flowers on naked 
shoots in early spring. Indian rhododendron. See 
Melastoma. 
Rhodomela (ro-dom'e-la), . [NL. (Agardh, 
1824), < Gr. />6Aov, rose,"+ fiftac., black.] A 
genus of marine alga? of the class Floridese 
and type of the suborder Rhodomeleie. The 
fronds are dark-red, filiform or subcompressed and pin- 
nately decompound, with filiform branches, the tetra- 
spores tripartite, the cystocarps sessile or pedicellate, 
and the spores pyriform. The genus is small, and mostly 
confined to high latitudes in both hemispheres. There 
are two species or forms on the New England coast. 
Rhodomelaceae (ro'do-me-la'se-e), n.pl. [NL. 
(Harvey, 1849), < Rhodomela -f- -acese.] Same 
as Rhodomelese. 
Rhodomeleae (ro-do-me'le-e), . pi. [NL. 
(Agardh, 1841), < Rhodomela + -ex.] A subor- 
der of florideous alg, named from the genus 
Rhodomela. This is the largest suborder of the Flori- 
dese, and contains many of the most beautiful seaweeds. 
It is characterized mainly by the cystocarpic fruit, which 
is external and has the spores borne separately on short 
stalks. The fronds are usually filiform and branching. 
rhoclomontade, a. and n. See rodomontade. 
rhodonite (ro'do-nlt), n. [Irreg. < Gr. /x5oW, 
rose, + -ife 2 .] ' Native manganese silicate, 
sometimes containing zinc or calcium : a min- 
eral occurring massive, 
rarely in distinct crys- 
tals, of a fine rose-red 
or pink color. It is 
sometimes used as an 
ornamental stone. 
Rhodope (ro'do-pe), n. 
[NL. (Kolliker, 1847), 
prob. < Gr. 'Pooom/, 
Rhodope, a Thracian 
nymph.] A remarkable 
genus, type of the fami- 
ly Rhodopidse, based on 
R. eertnii/i. This little crea- 
ture exhibits such equivocal 
characters that it has been 
considered by some as a pla- 
narian worm, by others as an 
abranchiate mollusk, though 
it has no odontophore. 
rhodophane (ro ' do- 
fan), n. [< Gr. p&Aov, 
rose, + -Qavr/c, appear- 
ing, < <t>aiv?afiai, appear.] 
A red pigment found in 
the retinal cones of the 
eyes of certain fishes, reptiles, and birds. The 
pi gnu-lit is held in solution by a fatty body. 
, top 
vera 
b. side view ; 
, . , 
longitudinal section (enlarged . 
5157 
rhodophyl, rhodophyll (ro'do-fil), . [< Gr. 
/xirffof, red, + pi'oi', a leaf.] The compound 
pigment of the red algse. 
rhodophyllite (ro-do-fil'lt), . [< Gr. jMo>>, 
rose, + <fi~f.M\; leaf, + -ite 2 .] In miiieriil., a va- 
riety of penninite from Texas in Pennsylvania, 
of a reddish color, and peculiar in containing a 
small percentage of chromium sesquioxid. 
rhodophyllous (ro-do-fil'us), a. [< rto&pMi 
+ -OHS.] In hot., containing rhodophyl; like 
rhodophyl. 
Cytioplasm mostly rhodophyttmix. 
H. C. Wood, Fresh-Water AlgK, p. 213. 
Rhodopidae (ro-dop'i-de), . pi. [NL., < Rh<>- 
<li>lic + -fcte.] A family of simple marine in- 
vertebrates of uncertain relationship, typified 
by the genus Rhodope. They are of an elongate flat- 
tened form, somewhat convex dorsally, and destitute of 
mantle, dorsal appendages, tentacles, branchiae, and odon- 
tophore. The digestive tube is very simple, and there is 
no pharynx, kidney, or heart. The family has been re- 
ferred to the nudibranchiate gastropods and to the tur- 
bellarians. See cut under Rhodope. 
rhodopsin (ro-dop'sin), n. [< Gr. podov, rose, 
+ di/Kf , view, + -in 2 .] Visual purple ; a pig- 
ment found in the outer segments of the reti- 
nal rods. It is quickly bleached by light, but the pur- 
ple color is regained by placing the pigment in the dark. 
In the normal retina it is restored by the action of the 
pigmentary layer of cells. 
Rhodora (ro-do'ra), n. [NL. (Duhamel du Mon- 
ceau, 1767), so called from the rose-colored 
flowers; < Gr. p66oi>, rose (see rose 1 ), the NL. 
word being based, as to form, on the L. rho- 
dora, a plant, Spirsea Clmaria or Arioicus, and 
said to be a Gallic word.] 1. A former genus 
of Ericaceae, now included in Rliododendron, 
section Azalea, but still giving name to the 
tribe Rhodorese. It was set apart chiefly on account 
of its prominently two-lipped flower, of which the lower 
lip consists of two petals, completely separate, or much 
more nearly so than the three divisions of the upper lip. 
There was but one species. See def. 2. 
2. [Z. c.] A low deciduous shrub, Rhododen- 
dron Rhodora (Rhodora Canadennis), a native of 
cold and wet wooded places from Pennsylvania 
northward, often covering acres with its delicate 
rosy flowers, which appear before the leaves. 
In May, when sea-winds pierced our solitudes, 
I found the fresh Rhodora in the woods, 
Spreading its leafless blooms in a damp nook; . . . 
The purple petals, fallen in the pool, 
Made the black water with their beauty gay. 
Emerson, The Rhodora. 
Rhodorese (ro-do're-e), n. pi [NL. (Don, 1834), 
< Rhodora -f'-e*.] 'A tribe of plants of the order 
Ericaceie, characterized by a septicidal eapsu- 
lar fruit, deciduous, imbricated, and common- 
ly gamopetalous corolla, and shrubby habit. 
It includes 16 genera, chiefly of northern regions and 
mountains, often very showy in blossom, as in the genera 
Rhododendron, Kalmia, Ledum, and Rhodothamnus. See 
Rhodora and Azalea. 
rhodosperm (rp'do-sperm), n. [< Rhodosper- 
mese.~\ An individual alga of the class Rhodo- 
spermese. 
Rhodospermese (ro-do-sper'mf-e), ti.pl. [NL. 
(Harvey), < Gr. /xJ<!oi,'rose, + airep/ia, seed.] A 
name employed by Harvey for the red or pur- 
ple algse, which are now placed under Agardh's 
older name Floridese. 
rhodospermin (ro-do-sper'min), 11. [< Gr. podov, 
rose, + oKipiia., seed, 4- -m 2 .] Crystalloids of 
proteid bodies found in the Floridese, forming 
the red coloring matter. 
Rhodosporeae (ro-do-spo're-e), w. pi. [NL., < 
Gr. p66ov, rose, + ojro/jof, seed, T -<.] Same as 
Bhodospermex. 
Rhodostaurotict (i'6"do-sta-rot'ik), . [Intend- 
ed as a translation into Gr. form of Rosicrucian; 
< Gr. p66ov, rose, + aravpof, cross, + -otic. Cf. 
Gr. <navpuTm6f, crossed, cruciform.] Rosicru- 
cian. 
Outis, . . . 
The good old hermit, that was said to dwell 
Here in the forest without trees, that built 
The castle in the air, where all the bretheren 
Rhodostattrotic live. 
B. Jonrnn, Masque of Fortunate Isles. 
Rhodostethia (ro-do-ste'thi-a), n. [NL. (Mac- 
gillivray, 1842), < Gr. p66ov, rose, + arf/Gof, the 
breast.] A genus of Laridee, so called from the 
rose-tint of the breast, unique in the family in 
having the tail cnneate ; the wedge-tailed gulls. 
Ross's rosy gull, R. rosea, is the only species, inhabiting the 
arctic regions. It was long regarded as one of the rarest 
uf birds, but has lately been found abundantly on the 
arctic coast of Alaska. It is white, rose-tinted, with black 
collar, wing-tips, ami bill, red feet, and pearl-blue man- 
tle ; the length is 14 inches. Also called flossier. See cut 
in next column. 
Rhodothamnus (ro-do-tham'nus), . [NL. 
(Keichenbach, 1830), < Gr. p&W, rose, + fht/jviu; 
rhomb 
Rosy or Wedge-tailed Gnll (Rhoiiostrthin rasfft'i. 
bush.] A genus of small shrubs of the order 
Ericacese, and tribe Rhodoreee. It is characterized by 
having a wheel-shaped corolla and ten long stamens, and 
terminal, solitary, and long-peduncled flowers. The only 
species, 7?. Chamsecistu*, is a native of the Austrian and 
Italian Alps. It is a low branching shrub with scattered 
short-petioled leaves, which are elliptical-lanceolate, en- 
tire, evergreen, and shining. It bears rose-colored flowers, 
large for the size of the plant, with spreading and curving 
stamens, the long slender peduncles and the calyx glan- 
dular-hairy. The whole plant in habit and flower resem- 
bles an azalea. The fruit is an erect flve-furrowed globose 
capsule. Sometimes called ground-cistus, translating the 
specific name. 
rhodotilite (ro-dot'i-lit), n. [< Gr. p6oov, rose, 
+ T/?.of, down, + -ite 2 .] A mineral found at 
Pajsberg in Sweden, having the same compo- 
sition as inesite. 
Rhodymenia (ro-di-me'ni-a), . [NL. (Greville, 
1830), < Gr. p66ov, rose, + lut/v, membrane: see 
hymen 2 .'] A genus of marine algse of the class 
Florideee, giving its name to the order Rhodyme- 
niaceie (which see for characters). See dulse, 
dillid: 
Rhodymeniaceae (ro-di-me-ni-a'se-e), n. pi. 
[NL., < Rhodynienia + -acex.] An order of no- 
rideous seaweeds of purplish or blood-red color. 
The root is disk-like or branched, much matted ; the frond, 
which is composed of polygonal cells, is either leafy or fili- 
form, and much branched, never articulate. The species 
are widely dispersed. Rhodymenia palmata, or dulse, is 
a well-known example. Many of the species of the genus 
Gracilaria are largely used in the East as ingredients in 
soups, jellies, etc., and as substitutes for glue. One of 
them is the ayar-agar of the Chinese. 
rhoeadic (re-ad'ik), a. [< NL. Rhceas (Rliaiad-) 
(see def.) (< Gr. potdf (poiaA-), a kind of poppy) 
+ -c.] Contained in or derived from the pop- 
py Papaver Rhatas. Rhoeadic acid, one of the color- 
ing principles in the petals of Papaver Rhceas. 
rhceadine (re'a-din), M. [<r/io-ori(/c) + -i'He 2 .] A 
crystallizable" alkaloid (C 2 iH 2 iNO 6 ) found in 
Papaver Rhceas. It is non-poisonous. 
rhoeagenine (re-aj'e-nin), n. [< NL. Rhceas (see 
rhceadic) + -yen + -t'we 2 .] A base, ispmeric 
with rhoeadine, found in acidified solutions of 
rhoeadine. 
rhomb (romb), n. [< OF. rhombe, F. rhombe = 
Sp. It. ronibo = Pg. rhombo, < L. rhombus, ML. 
also rhmnbus, nimbus, a magician's circle, a 
kind of fish, in LL. a rhomb in geometry. ML. 
also a point of the compass, < Gr. p6ft- . 
fioc, /M'/i/3of, a spinning-top or -wheel, a / \ 
magic wheel, a spinning or whirling / \ 
motion, also a rhomb in geometry, a ( 
lozenge, < p^jiuv, revolve, totter, na- \ / 
salized form of peireiv, sink, fall, be un- \ / 
steady. Doublet of rhumb, run/6.] 1. 
In geom., an oblique-angled equilateral 
parallelogram ; a quadrilateral figure whose 
sides are equal, and the opposite sides paral- 
lel, but the angles unequal, two being obtuse 
and two acute. 
See how in warlike muster they appear, 
In rhombs, and wedges, and half- moons, and wings. 
Milton, P. R., iii. SOS. 
2. In crystal., a solid bounded by six equal and 
similar rhombic planes ; a rhombohedron. 3. 
In zobl., a pair of semirhombs forming a rhom- 
bic figure, as certain plates of cystic crinoids. 
4. A material circle. [Rare.] 
That swift 
Nocturnal and diurnal rliomb suppos'd. 
Invisible else above all stars, the wheel 
Of day and night; which needs not thy belitf 
If earth, industrious of herself, fetch day 
Travelling east, and with her part averse 
Kmrn the sun's beam meet night, her other part 
Still luminous by his ray. Milton, P. L.. viii. 134. 
Fresnel'S rhomb, .1 rhomb of i-rown-glass, so cut that 
a ray of light entering one of its fares at riirbt angles shall 
fnierjre :lt right angles at the opposite face, after under- 
