, 270 
=. THE DICTIONARY OF GARDENING, 
Rafnia—continued. 
cuneate, lanceolate, linear-lanceolate, or linear-filiform, sub- 
obtuse or acute. Branchlets angular. h. lft. to 1ft. 1816. 
Sub-shrub. SYN. R. filifolia. 
R. elliptica (elliptic-leaved). A. peduncles axillary, one- 
flowered, with a pair of leafy bracts under the flower. June. 
l. 2in. to 3in. long, broadly obovate, elliptical, oblong, or ovate- 
lanceolate, acute or obtuse and mucronate ; upper ones narrow 
and more lanceolate, all narrowed at base. Branches angular. 
h. 1ft. to 3ft. 1819. Shrub. 
R. filifolia (thread-leaved). A synonym of R. angulata. 
R. trifiora (three-flowered).* jl., keel about twice as long as 
the calyx tube; peduncles axillary, one to three together, 
leafless, or branched and leaf-bearing. June. J. lin. to din. 
long, roundish-obovate, elliptical or ovate-lanceolate, acute or 
mucronulate, obtuse at base. Branches angular or two-edged. 
h. 2ft. to 4ft. 1784. Shrub, (B. M. 482, under name of 
Crotalaria triflora.) 
RAGGED ROBIN. See Lychnis Flos-cuculi. 
RAGWEED, or RAGWORT. See Senecio 
Jacobeza. 
RAGWORT. See Othonna. 
RAILLARDIA (named in honour of A. M. L. Raillard, 
an officer in the French Marine service), ORD. Composite. 
A genus comprising nine species of greenhouse shrubs, 
confined to the Sandwich Islands. Flower-heads yellow, 
rayless, mediocre or small, racemose or corymbose at the 
apices of the branches; involucre cylindrical or narrow- 
campanulate, with one series of connate or at length 
free bracts; receptacle small, convex or _ sub-conical, 
naked or setose-fimbrilliferous ; achenes narrow, glabrous, 
or slightly pilose. Leaves opposite, ternately whorled, 
or alternate, sessile, entire, coriaceous, at length shining. 
For culture of the only species introduced—now pro- 
bably lost to gardens—see Senecio. 
R. ciliolata (fringed-leaved). fl.-heads five to eight, clustered in 
a paniculate corymb; achenes sub-tetragonal, attenuated at 
base. July. i. ternately whorled, lanceolate, glabrous on both 
sides, rather more than 4in. long, shortly ciliated on the margins. 
Branches velvety-pubescent. h. 2ft. 1865. (B. M. 5517.) 
RAIN. A familiar example of the origin and nature 
of Rain is seen in the formation of a miniature shower, 
when steam escapes from a steam-engine into the air. 
When water is heated, it becomes an invisible vapour; 
and this rises, and mixes with the air, if the air is 
warm. When the warm air, full of water in this state, 
mixes with cold air, or touches any cold object, the 
vapour returns to the state of water; but; for a time, 
it remains in the form of very small particles, like fine 
dust—so light, that they can still float in the air. In 
this state, they form clouds when high above the earth, 
or mist when lying close to the earth. Among moun- 
tains, clouds and mists are often seen to be directly 
continuous. But mists often cling to the mountain-tops 
while the sky is nearly cloudless. This is owing to the 
rocks and soil being colder than the air, and causing 
the vapour to become visible as mist, by cooling the air 
near them below the temperature at which the water can 
remain vapour. As the wind carries the mist from the 
mountain into the warmer air around, it resumes the 
form of vapour, and becomes invisible; but new mist is 
formed, and supplies the place of that carried away, so 
that the mist seems to remain unchanged on the peaks for 
hours. Clouds form and disappear in the sky according 
as the air filled with vapour meets colder or warmer 
winds, When the minute drops of water that form clouds 
are very crowded, they join together, and form drops, 
too large to be supported in the air. These then fall as 
Rain. Sometimes, a cloud will be seen raining high up 
in the sky, though Rain does not reach the ground. This 
happens when the Rain has to fall through a layer of 
warm, dry air, in which it is all turned into vapour 
again. Light Rain sometimes falls out of a sky cloudless 
or nearly so; but this is a rare occurrence. The greater 
amount of rainfall during the night is due to the cooling 
of the air when the sun’s heat is withdrawn. The vapour 
= 
Rain—continued. 
forms drops of water, and falls as Rain. The sources 
of the vapour in the air are various. Much of it is 
given off by growing plants, and a little by animals. 
More is taken up by warm, dry winds blowing over the 
surface of the land, with its marshes, rivers, and lakes ; 
but most of all is absorbed by the winds in passing over’ 
the oceans, such as the Atlantic Ocean. Such winds are 
saturated, or nearly so; that is, they carry away as much 
vapour as they can dissolve at the temperature they had 
while passing over the water. If this is higher thn 
that of the land at which they first arrive, they will give 
up, as Rain, the vapour that no longer can be dissolved 
when the temperature falls. Hence, countries near oceans 
receive more Rain than those at a distance from them 
in the middle of continents. Mountainous countries near 
the sea are especially rainy, since air becomes colder 
the higher it rises along the slopes, and a very great 
part of the vapour is thus lost. For the reasons just 
stated, as well as from local peculiarities of situation, 
the frequency and amount of the rainfall varies widely 
in different localities, and at different seasons. The total 
amount of Rain that falls in any given time is measured 
by means of instruments (see Rain-gauge). Careful 
observations have been carried on in many countries, and 
in many localities, for a considerable number of years, 
as to the total amount of Rain that falls during the year, 
as well as during the various periods of the year, in 
each locality. The amount is expressed in the number 
of inches in depth that the Rain would reach in any given 
time, if it could all be confined to the exact area on 
which it has fallen. 
It has been found that, in some countries in the 
tropics, e.g., in Upper Egypt and the Sahara Desert, 
and on part of the coast of Peru, little Rain, if any, 
falls. On the other hand, the heaviest recorded rainfall 
occurs among mountain ranges in the neighbourhood of 
tropical oceans. Thus, in the Himalaya Mountains, 
about 100 miles from Calcutta, a rainfall of about 
524in., or about 44ft., has been observed within a year. 
In the British Islands, the rainfall is considerably 
greater on the west side than on the east, the winds 
from the Atlantic Ocean losing much of their vapour 
among the mountains. The heaviest rainfall in Britain 
is recorded from the Cumberland mountains, near Kes- 
wick, where over 150in., or 123ft., of Rain has been 
collected in a year. Along our western coasts, the 
average annual rainfall varies from about 36in. to 66in., 
and on the eastern side of our islands, from about 20in. 
to 30in. : 
But the actual rainfall does not bear any definite 
relation to the number of rainy days in a year, for often 
the heaviest fall is met with in districts where it is 
almost limited to certain seasons. When much Rain 
falls in a limited time, the greater part of it necessarily 
flows off the surface of the ground, and it is apt to 
carry away the fertile soil, and to cause disastrous 
floods. Where, on the other hand, the period during 
which it falls is more prolonged, the Rain sinks into 
the soil, and supplies the underground reservoirs of 
springs. ‘ 
In passing through the atmosphere, the rain becomes 
of the same temperature, and, as this in summer is 
almost always higher than that of the soil, the latter 
becomes warmed, and the plants in it are stimulated to 
more active growth. Moreover, the rain-water has 
oxygen, and, it may be, also minute traces of ammonia 
and of nitric acid, obtained from the atmosphere, dis- 
solved freely in it, and these also are beneficial, as 
food, to the roots of plants. It is unnecessary to dilate 
on the importance of a good supply of water in the 
soil, insured to plants by regular Rains. es 
Rain-water is very generally preferred for watering 
plants in pots, and it has the great advantage over 
