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CORRESPONDENCE. 343
as possible. Blue flowers in general do not require heat ; jou may put them
between sheets of plain white blotting-paper, five or six sheets on each side,
passing the stalks and calyces, as directed above, tlirough holes made in one of
the thicknesses, and subject them to just sufScient pressure to keep the flower
from wrinkling. In the same manner, Ferns, white, and some variegated -leaved
plants, such as Centaurea, Begonias, and Caladiums, may be treated. The
fancy-leaved Geraniums require heat ; but these, as well as other plants with
variegated foliage produced by high cultivation, will often fail to repay the most
careful treatment, as they are very apt to lose their distinctive markings under
the di-ying process. For mounting the flowers you require a sheet of white
cardboai'd, a pair of scissors or a penknife, gum, and a small camel-hair pencil.
The gum must be vei-y strong, and prepared as follows :—Take three oimces of
gum ai-abic ; pour upon it just sufficient hot water to dissolve it ; then add a
tablespoonfid of spirits of wine. The gi-eatest care and patience is required in
the manipulation of the flowers ;
they must be taken up between the blade of
your penknife and one finger. It is well to arrange them first on the card-
board without fastening them, and, having arrived at a satisfactory effect, to
fix the arrangement in your own mind ; then remove the flowers and proceed
to buQd up your design, gumming the flowers one by one in the position you
have assigned them. The smallest dab of gum in the middle of the back of the
flower or leaf is sufficient to hold it in its place, A cardboard mount, round
or oval, must now be placed on the cardboard on which the group is fixed, and
the whole covered with a sheet of glass, and fastened round the edges so as to
exclude the air. These groups may be framed as pictures, or mounted as fire-
screens and table-tops. If hung up as a picture, it must be on a wall looking
north ; and, however they are used, care must be taken that the sun's rays
shall not rest upou them. They must also be kept free fi'om damp."
COKRESPONDENCE.
On a Poisoning Solution for Botanical Specimens.
Great differences exist in the strength of the poisoning solutions for herbarium
specimens recommended in the various botanical text-books commonly
in use by students. Thus, Desvaus and De Candolle advised spirits of wine
wholly, Lindley the same, half saturated with corrosive subHmate, wliich latter
proportion could scarcely be much less than a seventh or eighth of the weight
of the spii'it ; Germain de Saint-Pierre directs the proportions to be 15 grammes
of sublimate to the Htre of spirit (nr 231-5103 grs. troy to 1'7608 imp. pints)
Duchartre, a solution of double this strength ;
whilst Balfour recommends half
a drachm of sublimate to each ounce of camphorated spirit or naphtha.
Dried plants are unusually subject to the attacks of insects in southern
China, especially diu-ing the south-west monsoon, when the temperature is
;