516 
THE DICTIONARY OF GARDENING, 
Orchid Fertilisation—continued. 
s lie almost side by side, and are covered by an 
ais membrane formed by the rostellum. This a 
brane prevents the disks from drying, which wo 
render them useless. It is at first continuous 51 
the disks, but it soon tears sei p% agi -r touched, 
it i ily d ed down, leaving them bare. 
7 l insect (e.g., a moth) visits the flowers, 
and conveys the pollen of one flower to the stigmas 
of the next one visited, it pushes the „proboscis down 
the tu of the labellum, and, in doing so, its pro- 
boscis, or its head, rubs against the membrane, and, 
depressing it, lays bare the sticky disks of the 8 
These, as soon as they are touched, adhere to the p 
with which they are in contact, and, on the insect with- 
drawing its head, one or both of the pollinia are 
also withdrawn, They are erect when first withdrawn, 
but, in about half a minute, as the disks dry, 550 
pollinia bend forward, and thus come to lie nearly 
alongside the proboscis, or other body, in the very 
FIG. 763. CYPRIPEDIUM CALCEOLUS. 
best position to bring them into contact with th 
of flowers visited later, Owing to the little interval 
that elapses before the pollinium is in the suitable 
position, the insect has usually visited all the flowers on 
a stem before any of the pollen could be left in flowers 
of the plant from which it was taken; hence, cross-fer- 
tilisation between different plants is favoured. When a 
pollinium touches a stigma, some of the small masses 
adhere, and are dragged off, and thus one pollinium 
suffices for several stigmas. Insects have frequently 
been taken bearing pollinia, and often several pollinia 
are found adhering to the proboscis and head of an 
insect. 
O. maculata, like most of this family, remains 
if insects are prevented from visiting the flowers, and 
e stigmas 
barren | 
Orchid Fertilisation—continued. 
id i ri i i here is no 
aid in transferring the pollen is not given. T i 
means in this plant of conveying pollen to the stigma, 
without extraneous help, and the adaptations for cross- 
fertilisation are complete. 
It may, therefore, be regarded as the type of a large 
section of Orchids, in so far as concerns its entire depen- 
dence on extraneous aid, though, in minor points, there is 
FIG. 764. SINGLE FLOWER OF CYPRIPEDIUM SPECTABILE. 
a considerable diversity in the methods of favouring cross- 
fertilisation; e.g., in 0. pyramidalis, the sticky disks 
àre united into a concave band, which adheres to the 
proboscis of the insect visitors. The pollinia pass throùgh 
the same change of position as in O. maculata. 
Listera ovata, the “ Twayblade,” which is an incon- 
spicuous, greenish Orchid, growing in grassy places, 
has the pollen masses lying immediately above the ros- 
tellum. The pollen masses are dry, and, therefore, cannot 
adhere of themselves to insects; but when the tip of the 
rostellum is touched, even very gently, by the insect, a 
drop of sticky fluid oozes out, and fixes the pollen grains 
