by C.K. Sprengel, in which he clearly proved by innumerable
observations, how essential a part insects play in the fertilisation of
many plants. But he was in advance of his age, and his discoveries were
for a long time neglected. Since the appearance of my book on Orchids,
many excellent works on the fertilisation of flowers, such as those by
Hildebrand, Delpino, Axell and Hermann Muller, and numerous shorter
papers, have been published. (1/3. Sir John Lubbock has given an
interesting summary of the whole subject in his 'British Wild Flowers
considered in relation to Insects' 1875. Hermann Muller's work 'Die
Befruchtung der Blumen durch Insekten' 1873, contains an immense number
of original observations and generalisations. It is, moreover,
invaluable as a repertory with references to almost everything which has
been published on the subject. His work differs from that of all others
in specifying what kinds of insects, as far as known, visit the flowers
of each species. He likewise enters on new ground, by showing not only
that flowers are adapted for their own good to the visits of certain
insects; but that the insects themselves are excellently adapted for
procuring nectar or pollen from certain flowers. The value of H.
Muller's work can hardly be over-estimated, and it is much to be desired
that it should be translated into English. Severin Axell's work is
written in Swedish, so that I have not been able to read it.) A list
would occupy several pages, and this is not the proper place to give
their titles, as we are not here concerned with the means, but with the
results of cross-fertilisation. No one who feels interest in the
mechanism by which nature effects her ends, can read these books and
memoirs without the most lively interest.

From my own observations on plants, guided to a certain extent by the
experience of the breeders of animals, I became convinced many years ago
that it is a general law of nature that flowers are adapted to be