s yet been suggested but the need
of attracting insects to cross-fertilise them; yet the attractiveness of
regular flowers with bright colours and an ample supply of nectar is
equally great, and cross-fertilisation can be quite as effectively
secured in these by any of the four simple methods already described.
Before attempting to suggest a possible solution of this difficult
problem, we have yet to pass in review a large body of curious
adaptations connected with insect fertilisation, and will first call
attention to that portion of the phenomena which throw some light upon
the special colours of flowers in their relation to the various kinds of
insects which visit them. For these facts we are largely indebted to
the exact and long-continued researches of Professor Hermann Mueller.

_Summary of Additional Facts bearing on Insect Fertilisation._

1. That the size and colour of a flower are important factors in
determining the visits of insects, is shown by the general fact of more
insects visiting conspicuous than inconspicuous flowers. As a single
instance, the handsome Geranium palustre was observed by Professor
Mueller to be visited by sixteen different species of insects, the
equally showy G. pratense by thirteen species, while the smaller and
much less conspicuous G. molle was visited by eight species, and G.
pusillum by only one. In many cases, however, a flower may be very
attractive to only a few species of insects; and Professor Mueller
states, as the result of many years' assiduous observation, that "a
species of flower is the more visited by insects the more conspicuous it
is."

2. Sweet odour is usually supplementary to the attraction of colour.
Thus it is rarely present in the largest and most gaudily coloured
flowers which inhabit open places, such as poppies, paeonies,
sunflowers, and many others; while it is often the accompaniment of
inconspicuous flowers, as the mignonette; of such as grow in shady
places, as the violet and primrose; and especially of white or yellowish
flowers, as the white jasmine, clematis, stephanotis, etc.

3. White flowers are often fertilised by moths, and very frequently give
out their scent only by night, as in our butterfly-orchis (Habenaria
chlorantha); and they sometimes open only at night, as do many of the
evening primroses and other flowers. These flowers are often long tubed
in accordance with the length of the moths' probosces, as in the genus
Pancratium, our bu