INSECTS AND ELOWEES. 
123 
which collect pollen without moistening it ; and these may be- 
observed to perform both operations simultaneously. 
The mode of fertilisation of the Orchidese and Asclepi- 
adeoe has been made so familiar by the writings of Darwin and 
others, that no detailed description will be necessary. With 
the exception of the Bee-orchis, orchids are almost invariably 
entomophilous ; and the parts of the flowers are so arranged 
that in obtaining the honey from the nectary (the spur or 
labellum) the visiting insect — mostly some species of Hy- 
menoptera or Lepidoptera — must necessarily strike its. head or 
proboscis, in the first flower which it visits, against the viscid 
disc, so as to detach the pollinia or pollen-masses ; while on 
entering another flower these pollen-masses are made to strike 
against the stigmatic surface. Fig. 6 shows at a a drawing of 
the common tway-blade, Listera ovata , copied from the 
frontispiece ofSprengel’s “ Entdeckte Geheimniss der Natur ; ” 
and at b another flower, in which the honey is being sucked 
from the spur by a species of ichneumon, illustrating how 
admirably the two long arms into which the labellum is 
divided are fitted for affording a standing-place to the insect 
while -obtaining the honey. 
A plant which it is difficult to place in any class in relation 
to the mode of its fecundation is the Vcdlisneria spiralis , of 
the South of France, so commonly grown in fresh-water 
aquaria. The pollination of the pistil is effected in this 
instance neither by the agency of insects nor by that of the 
wind, but as it were spontaneously through the medium of 
water. The plant is dioecious, the male and female flowers 
(fig. 7, m and/) being both of very simple structure and borne 
on different plants, often growing in close proximity to one 
another. The male flowers are borne on very short stalks, the 
female flowers on much longer spiral stalks, which have the 
power of coiling and uncoiling. When mature the male flowers 
break off from their pedicels, and, rising to the top of the 
water, scatter the pollen abroad on its surface, as if waiting the 
arrival of the female flowers, which, about the same time, also 
rise to the surface by the uncoiling of their pedicels. In this 
position some of the floating pollen reaches them and fertilises 
the pistil ; and when this has been accomplished the pedicel 
again coils up and brings the female flower again below the 
surface of the water, where it ripens its fruit. 
These, examples will serve only as a few illustrations of the 
vast field still left for observers of the phenomena connected 
with the contrivances supplied by nature to favour the cross- 
fertilisation of flowers. 
