ORCHIDACEAE 
493 
here ; in the description of the individual genera other more detailed 
features are treated. Very few of the order secrete free honey ; in 
most cases the insect has to bite into or drill the tissue for the juice 
therein contained ; this tissue is usually part of the labellum — often a 
spur at the base — or the basal part of the column. The pollinia are 
removed as a rule when the insect is going out of the fir. In most 
cases the insect in entering displaces the rostellum or some portion of 
it, and thereby exposes and comes into contact with a sticky mass 
(due to disorganisation of cells formerly living). This becomes 
cemented to the insect while it is drilling for honey, and as the insect 
goes out again it takes with it the viscid lump, together with the 
pollinia, either merely glued to it, or attached by caudicles. In 
many cases the pollinia are in such a position that when the insect 
enters the next flr. they will touch the stigmas. In others this is not 
so, e.g . Orchis, where the anthers and stigma are far apart on the 
column, and in such cases the pollinia, on getting out of the anther, 
execute a hygroscopic movement which brings them into the proper 
position on the insect’s body to strike the stigmas. Such is the 
general principle of the orchid mechanism, but the variety in detail 
is endless. Many firs, have the most extraordinary devices, e.g . 
Coryanthes, Stanhopea, Vanda, &c. See under individual genera. 
The fruit is a capsule, containing usually a gigantic number of 
exceedingly small and light seeds, which are well suited to wind 
distribution (hence, among other causes, the epiphytic habit of so 
many of the order). It may be noted that, as Darwin has pointed 
out, this production of immense numbers of seeds is an evidence of 
lowness of organisation, and contradicts the impression that would 
otherwise be derived from the floral complications. 
The O. are favourites in horticulture, but Vanilla is the only one 
of economic importance. 
Classification and chief genera (after Pfitzer) : — 
A. DIANDRAE (two stamens). 
1. Apostasiinae : Apostasia. 
2. Cypripedilinae : Cypripedium. 
B. MONANDRAE (one stamen). 
a. BASITONAE (basitonic, anther not falling off) : 
3. Ophrydinae : Ophrys, Orchis, Habenaria, Disa. 
b. A CROTONAE (acrotonic, anther usually falling easily) : 
a. Acranthae (acranthous sympodial) : 
I. Convolutae (leaves convolute in bud, with no dis- 
tinction between blade and sheath) : 
4. Neottiinae: Vanilla, Epipactis, Neottia. 
II. Articulatae (as I., but with a joint between blade 
and sheath) : 
5. Thuniinae : Thunia, Trichosma. 
6. Coelogyninae : Coelogyne, Pholidota. 
