gales that blow in autumn on its expanded form. M. Richard explains
the cause more philosophically: "Although the fall of the leaves
generally takes place at the approach of winter, cold is not to be
considered as the principal cause of this phenomenon. It is much more
natural to attribute it to the cessation of vegetation, and the want
of nourishment which the leaves experience at that season, when the
course of the sap is interrupted. The vessels of the leaf contract,
dry up, and soon after, that organ is detached from the twig on which
it had been developed."

Why do some trees, as the Oak, the Beech, and the Hornbeam, retain
their leaves to a late period of autumn?

Because the life of the twigs on which they grow is not sufficiently
vigorous to throw them off, after the brown colour indicates that they
are dead.

Why have some plants been termed the Poor Man's Weather-glass?

Because they shut up their flowers against the approach of rain.
Linnaeus, however, thinks, that flowers lose their fine sensibility,
after the anthers have performed their office, or when deprived of
them artificially. Sir James Smith also observes, that some species
are sometimes exhausted by continued wet; "and it is evident that
very sudden thunder showers often take such flowers by surprise, the
previous state of the atmosphere not having been such as to give them
due warning."

Many flowers have a regular time of opening and shutting. We have
already mentioned the Marigold; the goat's-beard is vulgarly called