by, _Catalogue of Neuroptera Odonata_
(London, 1890). For habits and details of transformation and larval
life, see L. C. Miall, _Natural History of Aquatic Insects_ (London,
1895); H. Dewitz, _Zool. Anz._ xiii. (1891); and J. G. Needham, _Bull.
New York Museum_, lxviii. (1903). For geographical distribution, G. H.
Carpenter, _Sci. Proc. R. Dublin Soc._ viii. (1897). For British
species, W. J. Lucas, _Handbook of British Dragonflies_ (London,
1899). For wings and mechanism of flight, R. von Lendenfeld, _S.B.
Akad. Wien_, lxxxiii. (1881), and J. G. Needham, _Proc. U.S. Nat.
Mus._ xxvi. (1903). For general morphology, R. Heymons, _Abhandl. k.
preuss. Akad._ (1896), and _Ann. Hofmus. Wein_, xix. (1904).
(R. M'L.; G. H. C.)

FOOTNOTE:

[1] A similar contrivance was suggested and (if the writer mistakes
not) actually tried as a means of propelling steamships.

DRAGON'S BLOOD, a red-coloured resin obtained from several species of
plants. _Calamus draco_ (Willd.), one of the rotang or rattan palms,
which produces much of the dragon's blood of commerce, is a native of
Further India and the Eastern Archipelago. The fruit is round, pointed,
scaly, and the size of a large cherry, and when ripe is coated with the
resinous exudation known as dragon's blood. The finest dragon's blood,
called _jernang_ or _djernang_ in the East Indies, is obtained by
beating or shaking the gathered fruits, sifting out impurities, and
melting by exposure to the heat of the sun or by placing in boiling
water; the resin thus purified is then usually moulded into sticks or
quills, and after being wrapped in reeds or palm-leaves, is ready for
market. An impurer and inferior kind, sold in lumps of considerable
size, is extracted from the fruits by boiling. Dragon's blood is dark
red-brown, nearly opaque and brittle, contains small shell-like flakes,
and gives when ground a fine red powder; it is soluble in alcohol,
ether, and fixed and volatile oils. If heated it gives off benzoic acid.
In Europe it was once valued as a medicine on account of its astringent
properties, and is now used for colouring varnishes and lacquers; in
China, where it is mostly consumed, it is employed to give a red facing
to writing paper. The drop dragon's blood of commerce, called _cinnabar_
by Pliny (_N.H._ xxxiii. 39), and _sangre de dragon_ by Barbosa was
formerly and is still one of the products of Socotra, and is obtained
from _Draca