THE BEHAVIOUR OF PLANTS 29 
and form three hollow boats, by means of which the flower 
floats freely, while the two functional stamens project upwards 
and somewhat obliquely into the air, exposing the large sticky 
pollen-cells. Blown hither and thither by the wind, these 
little flower-boats “‘accumulate in the neighbourhood of fixed 
bodies, especially in their recesses, where they rest like ships 
in harbour. When the little craft happen to get stranded 
in the recesses of a female Valisneria flower, they adhere to 
the tri-lobed stigma, and some of the pollen-cells are sure to 
be left sticking to the fringes on the margins of the stigmatic 
surface.” * 
This is a good example of purely organic behaviour ad- 
mirably adapted to secure a definite and important biological 
end. Few will be likely to contend that it is even accom- 
panied by, still less under the guidance of, any conscious fore- 
sight on the part of the plant. And the lesson it should teach 
is that, in the study of organic behaviour, adaptation to the 
conditions of existence is not necessarily the outcome of 
conscious guidance. 
It is well known that the orchids exhibit, in their mode 
of fertilization, remarkable adaptations by which the visits of 
insects are rendered subservient to the needs of the plant. In 
the Catasetums, for example, the male flower may be described 
as consisting of two parts—a lower part, the cup-like labellum 
(Figs. 9, 2), which constitutes a landing-stage on which insects 
may alight; and an upper part, the column (Fig. 9, c), 
surrounded by the upper sepal and petals. In the upper part 
of the column the pollen-masses are borne at one end of an 
elastic pedicel, at the other end of which is an adhesive disc, 
and the rod is bent over a pad so as to be in a state of strain. 
The disc is retained in position by a membrane with which 
two long tubular horns (Figs. 9,2; 10, av) are continuous. 
These project over the labellum, where insects alight to 
gnaw its sweet fleshy walls, and if they be touched, even very 
lightly, they convey some stimulus to the membrane which 
surrounds and connects the disc with the adjoining surface, 
* Kerner, “ Natural History of Plants,” vol. ii., p. 132. 
