rtilisation of Plants_, 1876.]

[Footnote 145: See Darwin's _Fertilisation of Orchids_ for the many
extraordinary and complex arrangements in these plants.]

[Footnote 146: The English reader may consult Sir John Lubbock's
_British Wild Flowers in Relation to Insects_, and H. Mueller's great and
original work, _The Fertilisation of Flowers_.]

[Footnote 147: Mueller's _Fertilisation of Flowers_, p. 248.]

[Footnote 148: "Alpenblumen," by D.H. Mueller. See _Nature_, vol. xxiii.
p. 333.]

[Footnote 149: This peculiarity of local distribution of colour in
flowers may be compared, as regards its purpose, with the recognition
colours of animals. Just as these latter colours enable the sexes to
recognise each other, and thus avoid sterile unions of distinct species,
so the distinctive form and colour of each species of flower, as
compared with those that usually grow around it, enables the fertilising
insects to avoid carrying the pollen of one flower to the stigma of a
distinct species.]

[Footnote 150: See H. Mueller's _Fertilisation of Flowers_, p. 18.]

[Footnote 151: The above examples are taken from Rev. G. Henslow's paper
on "Self-Fertilisation of Plants," in _Trans. Linn. Soc._ Second series,
_Botany_, vol. i. pp. 317-398, with plate. Mr. H.O. Forbes has shown
that the same thing occurs among tropical orchids, in his paper "On the
Contrivances for insuring Self-Fertilisation in some Tropical Orchids,"
_Journ. Linn. Soc._, xxi. p. 538.]

[Footnote 152: These are the numbers given by Darwin, but I am informed
by Mr. Hemsley that many additions have been since made to the list, and
that cleistogamic flowers probably occur in nearly all the natural
orders.]

[Footnote 153: For a full account of cleistogamic flowers, see Darwin's
_Forms of Flowers_, chap. viii.]

[Footnote 154: Henslow's "Self-Fertilisation," _Trans. Linn. Soc._
Second series, _Botany_, vol. i. p. 391.]

[Footnote 155: The Rev. George Henslow, in his _Origin of Floral
Structures_, says: "There is little doubt but that all wind-fertilised
angiosperms are degradations from insect-fertilised flowers....
_Poterium sanguisorba_ is anemophilous; and _Sanguisorba officinalis_
presumably was so formerly, but has reacquired an entomophilous habit;
the whole tribe Poterieae being, in fact, a degraded group which has
descended from Potentilleae. Plantains retain their corolla but in a
degraded form. Junceae are degraded Lilies; while Cyperaceae and
Gram