Page:On the Various Contrivances by Which British and Foreign Orchids are Fertilised by Insects, and on the Good Effects of Intercrossing.djvu/1

 ON

THE VARIOUS CONTRIVANCES

BY WHICH

BRITISH AND FOREIGN ORCHIDS

ARE

FERTILISED BY INSECTS,

AND ON THE GOOD EFFECTS OF INTERCROSSING.

BY CHARLES DARWIN, M.A., F.R.S., &c.

WITH ILLUSTRATIONS.

LONDON:

JOHN MURRAY, ALBEMARLE STREET. 1862.

The right of Translation is reserved.

CHAPTER I.

Structure of Orchids—Power of movement of the pollinia—Perfect adaptation of the parts in Orchids pyramidalis—On the insects which visit Orchids, and on the frequency of their visits—On the fertility and sterility of several Orchids—On the secretion of nectar, and on moths being purposely delayed in obtaining it

CHAPTER II.

Ophree continued—Fly and Spider Ophrys—Bee Ophrys, apparently adapted for perpetual self-fertilisation, but with paradoxical contrivances for intercrossing—The Frog Orchids; fertilisation effected by nectar secreted from two parts of the labellum—Gymnadenia conopsea—reater and Lesser Butterfly Orchids; their differences and means of fertilisation—Summary on the powers of movement in the pollinia

CHAPTER III.

Epipactis palustris; curious shape of the labellum and its apparent importance in the fructification of the flower—Cephalanthera grandiflora; rostellum aborted; early penetration of the pollen-tubes; case of imperfect self-fertilisation; fertilisation aided by insects—Goodyera repens—Spiranthes autumnalis; perfect adaptation by which the pollen of a younger flower is carried to the stigma of an older flower on another plant

CHAPTER IV.

Malaxis paludosa; simple means of fertilisation—Listera ovata; sensitiveness of the rostellum; explosion of viscid matter; action of insects; perfect adaptation of the several oegans—Listera cordata—Neottia nidusavis; its fertilisation effected in the same manner as in Listera

CHAPTER V.

Cattleya, simple manner of fertilisation- Masdevallia, curious closed flower—Dendrobium, contrivance for self-fertilisation- Vandee, diversified structure of the pollinia; importance of the elasticity of the pedicel; its power of movement- Elasticity and strength of the caudicle—Calanthe with lateral stigmas, manner of fertilisation- Angnecum sesquipedale, wonderful length of nectary—Acropera, perplexing case, a male Orchid