THE AUSTRALIAN NATURALIST, ; 77 
very light pollen grains, sometimes, as in a few pines, 
winged. The stigma is usually much divided, so as to 
expose aS large a surface as possible to the chances of 
being reached by the flying pollen grains. 
The living things concerned in carrying pollen are— 
(1) Insects; (2) snails; (3) birds; and (4) mammals; 
but the bulk of the work is done by the first and third» 
groups. But insects and birds do not work for nothing, 
and so the plants have to provide some attraction for 
them. There is no altruism below the primates (and not 
so much among them as one might desire to see). The 
means of attraction are—(1) Colour; (2) scent; and (3) 
nectar, or some other food. 
colour, some on scent, and some use both as an advertise- 
ment. I think there can be no doubt but that insects are 
attracted by colour, although Plateau and other biolo- 
gists have tried to show that this is not so. But I have 
no doubt at all that it does. Both Mr. T. Steel and my- 
self have recorded a number of instances of moths and 
butterflies being attracted by coloured objects. And - 
there are other recorded cases. 
The signboards of colour and scent ‘would soon be 
disregarded if there were no reward, and the nectar pro- 
vides this; or, in the case of pollen- eating insects, the 
Some flowers depend upon 
pollen. Colour for attraction is usually found in the 
petals, but sometimes it is the sepals, sometimes bracts, 
as in Bougawmvitlea and Poinsettia, and even in the leaves 
subtending the flowers, as in a beautiful Brunsfelsia com- 
mon in the Botanic Gardens. In the case of small indi- 
vidual flowers, the advertising effect is got by massing : 
them together; as in the snow-bush and the black-thorn. 
The nectar again may be produced by any part, but 
usually it comes from glands in the centre of the flower. 
Wherever it is produced, it is always in such a position 
that an insect feeding on it brushes against the anthers 
and takes up pollen. 
Very many flowers are of a generalised type, and 
may be pollinated by almost any insect visitor. But 
there are also large numbers of flowers which are speci- 
ally adapted to be pollinated by certain groups of insects, 
or even by a single species. The same may be said of 
some flowers which ¢an only be pollinated by one species _ 
of bird. 
