f aloe furnished with leaves,
which, like the wild pine and Banana, hold water; and thence afford
necessary refreshment to travellers in hot countries. Nepenthes had a
bucket for the same purpose at the end of every leaf, Burm. Zeyl. 41.
17.]

_Four_ silvan youths in crystal goblets bear
The untasted treasure to the grateful fair;
Pleased from their hands with modest grace she sips,
And the cool wave reflects her coral lips.

375 With nice selection modest RUBIA blends,
Her vermil dyes, and o'er the cauldron bends;
Warm 'mid the rising steam the Beauty glows,
As blushes in a mist the dewy rose.

[_Rubia._ l. 375. Madder. Four males and one female. This plant is
cultivated in very large quantities for dying red. If mixed with the food
of young pigs or chickens, it colours their bones red. If they are fed
alternate fortnights with a mixture of madder, and with their usual food
alone, their bones will consist of concentric circles of white and red.
Belchier. Phil. Trans. 1736. Animals fed with madder for the purpose
of these experiments were found upon dissection to have thinner gall.
Comment. de rebus. Lipsiae. This circumstance is worth further attention.
The colouring materials of vegetables, like those which serve the purpose
of tanning, varnishing, and the various medical purposes, do not seem
essential to the life of the plant; but seem given it as a defence
against the depredations of insects or other animals, to whom these
materials are nauseous or deleterious. To insects and many smaller
animals their colours contribute to conceal them from the larger ones
which prey upon them. Caterpillars which feed on leaves are generally
green; and earth-worms the colour of the earth which they inhabit;
Butterflies which frequent flowers, are coloured like them; small birds
which frequent hedges have greenish backs like the leaves, and light
coloured bellies like the sky, and are hence less visible to the hawk,
who passes under them or over them. Those birds which are much
amongst flowers, as the gold-finch (Fringilla carduelis), are furnished
with vivid colours. The lark, partridge, hare, are the colour of the dry
vegetables or earth on which they rest. And frogs vary their colour with
the mud of the streams which they frequent; and those which live on
trees are green. Fish, which are generally suspended in water, and
swallows, which are generally suspended in air