ion necessary was to allow no
mixture of any unctuous materials, which destroyed the efficacy of the
soap. A vegetable soap, which has been found excellent for washing
silk, &c, may be thus obtained. To one part of the skin of the Ackee
add one and a half part of the _Agave karatu_, macerated in one part
of boiling water for twenty-four hours, and with the extract from this
decoction mix four per cent. of rosin. In Brazil, soap is made from
the ashes of the bassura or broom plant (_Sidu lanceolata_) which
abounds with alkali. There are also some soap barks and pods of
native plants used in China. Several other plants have been employed
in different countries as a substitute for soap. The bark of _Quillaia
saponaria_ renders water frothy and is used as a detergent by wool
dyers. _Saponaria vaccana_ is common in India. The pericarp of
_Sapindus emarginatus_ mixed with water froths like soap. Saponaceous
berries are found in Java.

The soap-worts to which the genus Sapindus belongs are tropical
plants. The fruit of many species of _Sapindus_ is used as a
substitute for soap, as _Sapindus acuminata_, _Laurifolius
emarginatus_ and _detergens_, all East Indian plants.

SECTION VI.

PLANTS YIELDING DRUGS, INCLUDING NARCOTICS AND OTHER COMMON MEDICINAL
SUBSTANCES.

The chief plants furnishing the drugs of commerce, and which enter
largely into tropical agriculture, are the narcotic plants, especially
tobacco, the poppy for opium, and the betel nut and leaf; as
masticatories--but there are very many others to which the attention
of the cultivator may profitably be directed. I have already trenched
so largely upon my space, that I cannot do that justice to the plants
coming under this section I could have wished. There are very many,
however, of which I must make incidental mention. Some few medicinal
plants have been already alluded to in former sections, particularly
in that on dye-stuffs, &c.

THE COCA PLANT grows about four or five feet high, with pale bright
green leaves, somewhat resembling in shape those of the orange tree.
The leaves are picked from the trees three or four times a year, and
carefully dried in the shade; they are then packed in small baskets.
The greatest quantity is grown about 30 leagues from Cicacica, among
the Yunnos on the frontiers of the Yunghos. Some is also cultivated
near to Huacaibamba.

The natives in several parts of Peru chew these leaves as Europeans do
tobacco, particularly