d by night-flying
insects would derive no advantage from being open by day; and on the
other hand, that those which are fertilised by bees would gain nothing
by being open at night. Nay it would be a distinct disadvantage, because
it would render them liable to be robbed of their honey and pollen, by
insects which are not capable of fertilising them. I have ventured to
suggest then that the closing of flowers may have reference to the
habits of insects, and it may be observed also in support of this, that
wind-fertilised flowers do not sleep; and that many of those flowers
which attract insects by smell, open and emit their scent at particular
hours; thus Hesperis matronalis and Lychnis vespertina smell in the
evening, and Orchis bifolia is particularly sweet at night.

But it is not the flowers only which "sleep" at night; in many species
the leaves also change their position, and Darwin has given strong
reasons for considering that the object is to check transpiration and
thus tend to a protection against cold.

BEHAVIOUR OF LEAVES IN RAIN

The behaviour of plants with reference to rain affords many points of
much interest. The Germander Speedwell (Veronica) has two strong rows of
hairs, the Chickweed (Stellaria) one, running down the stem and thus
conducting the rain to the roots. Plants with a main tap-root, like the
Radish or the Beet, have leaves sloping inwards so as to conduct the
rain towards the axis of the plant, and consequently to the roots;
while, on the contrary, where the roots are spreading the leaves slope
outwards.

In other cases the leaves hold the rain or dew drops. Every one who has
been in the Alps must have noticed how the leaves of the Lady's Mantle
(Alchemilla) form little cups containing each a sparkling drop of icy
water. Kerner has suggested that owing to these cold drops, the cattle
and sheep avoid the leaves.

MIMICRY

In many cases plants mimic others which are better protected than
themselves. Thus Matricaria Chamomilla mimics the true Chamomile, which
from its bitterness is not eaten by quadrupeds. Ajuga Chamaepitys mimics
Euphorbia Cyparissias, with which it often grows, and which is protected
by its acrid juice. The most familiar case, however, is that of the
Stinging and the Dead Nettles. They very generally grow together, and
though belonging to quite different families are so similar that they
are constantly mistaken for one another. Some Orchids have a curious
resembl