POLLINATION 
59 
effect its own (self-) pollination without assistance from any 
of them, but is dependent upon their help for cross-pollina- 
tion. Of existing flowers a small number are only cross- 
pollinated (if pollinated at all), having by mechanical or 
physiological means lost all power of self-pollination ( auto- 
gamy ). Others again are solely self-pollinated, having no 
arrangements for utilising in their service either wind or 
insects. The majority of flowers occupy an intermediate 
position between these two extremes ; they have arrange- 
ments, more or less perfect, for obtaining cross-pollination 
by external agents, while at the same time they are not so 
constructed as to be unable to perform self-pollination. 
There is reason for supposing the primeval angiosper- 
mous flowers to have been cross-pollinated. There are 
many purely self-pollinated flowers now existing, but it is 
more easy to explain their features on the supposition of 
their descent from cross-pollinated ancestry than to suppose 
them primitively autogamous. Most of the striking examples 
occur in families or even in genera most of whose members 
are cross-pollinated. There is a price to be paid for cross- 
pollination, and if the gain from the process should by any 
means become less than the cost, the plant may perhaps 
revert to self-pollination. It is easy to imagine cases in 
which this might occur. Suppose an insect-pollinated 
species, A, in a certain district and suppose a new and 
attractive flower, B, to arrive from another district and 
establish itself ; this will draw off some of the visitors of A 
and perhaps upset the balance of gain and loss, causing the 
latter to exceed the former. We shall then perhaps find A 
tending in the direction of increased autogamy ; the result 
will probably be the gradual reduction of those characters 
by which its visitors were attracted, and it may gradually 
almost entirely lose them. 
Suppose, however, that the introduction of B merely 
reduced A’s profit but did not destroy it, then we might 
imagine A increasing its expenditure, so to speak, upon 
attractive characters, so as if possible to regain its former 
predominance. This will perhaps only be possible in 
plants which have stores of reserve-materials to draw upon, 
capitalists , as they have been termed, in contrast to annuals, 
&c. which have no reserves ( proletarians ). The balance 
