XI 
THE SPECIAL COLOURS OF PLANTS 
321 
(Phormium tenax), are cross-fertilised by birds ; while in Natal 
the fine trumpet-creeper (Tecoma capensis) is fertilised by 
Nectarineas. 
The great extent to which insect and bird agency is 
necessary to flowers is well shown by the case of New 
Zealand. The entire country is comparatively poor in species 
of insects, especially in bees and butterflies which are the 
chief flower fertilisers; yet according to the researches of 
local botanists no less than one-fourth of all the flowering 
plants are incapable of self-fertilisation, and, therefore, wholly 
dependent on insect or bird agency for the continuance of 
the species. 
The facts as to the cross-fertilisation of flowers which have 
now been very briefly summarised, taken in connection with 
Darwin’s experiments proving the increased vigour and fer¬ 
tility given by cross-fertilisation, seem amply to justify his 
aphorism that “ Nature abhors self-fertilisation,” and his more 
precise statement, that, “No plant is perpetually self-fertil¬ 
ised ; ” and this view has been upheld by Hildebrand, Delpino, 
and other botanists. 1 
Self-Fertilisation of Flowers. 
But all this time we have been only looking at one side of 
the cpiestion, for there exists an abundance of facts which 
seem to imply, just as surely, the utter uselessness of cross¬ 
fertilisation. Let us, then, see what these facts are before pro¬ 
ceeding further. 
1. An immense variety of plants are habitually self-fer¬ 
tilised, and their numbers probably far exceed those which 
are habitually cross-fertilised by insects. Almost all the very 
small or obscure flowered plants with hermaphrodite flowers 
are of this kind. Most of these, however, may be insect 
fertilised occasionally, and may, therefore, come under the rule 
that no species are perpetually self-fertilised. 
2. There are many plants, however, in which special 
arrangements exist to secure self-fertilisation. Sometimes the 
corolla closes and brings the anthers and stigma into contact; 
in others the anthers cluster round the stigmas, both maturing 
together, as in many buttercups, stitchwort (Stellaria media), 
1 See H. Muller’s Fertilisation of Flowers, p. 18. 
Y 
