RIUMS.--The most exact descriptions,
accompanied with the most perfect figures, leave still something to be
desired by him who wishes to know completely a natural being. This
nothing can supply but the autopsy or view of the object itself. Hence
the advantage of being able to see plants at pleasure, by forming dried
collections of them, in what are called herbariums.

A good practical botanist, Sir J.E. Smith observes, must be educated
among the wild scenes of nature, while a finished theoretical one
requires the additional assistance of gardens and books, to which must
be superadded the frequent use of a good herbarium. When plants are well
dried, the original forms and positions of even their minutest parts,
though not their colours, may at any time be restored by immersion in
hot water. By this means the productions of the most distant and various
countries, such as no garden could possibly supply, are brought together
at once under our eyes, at any season of the year. If these be assisted
with drawings and descriptions, nothing less than an actual survey of
the whole vegetable world in a state of nature, could excel such a store
of information.

With regard to the mode or state in which plants are preserved,
desiccation, accompanied by pressing, is the most generally used. Some
persons, Sir J.E. Smith observes, recommend the preservation of
specimens in weak spirits of wine, and this mode is by far the most
eligible for such as are very juicy: but it totally destroys their
colours, and often renders their parts less fit for examination than by
the process of drying. It is, besides, incommodious for frequent study,
and a very expensive and bulky way of making an herbarium.

The greater part of plants dry with facility between the leaves of
books, or other paper, the smoother the better. If there be plenty of
paper, they often dry best without shifting; but if the specimens are
crowded, they must be taken out frequently, and the paper dried before
they are replaced. The great point to be attended to is, that the
process should meet with no check. Several vegetables are so tenacious
of their vital principle, that they will grow between papers; the
consequence of which is, a destruction of their proper habit and colors.
It is necessary to destroy the life of such, either by immersion in
boiling water or by the application of a hot iron, such as is used for
linen, after which they are easily dried. The practice of appl