TllK l"KirriI.lS.\'lM(»N ol' KLoWKKS liY INSKCTS. 
103 
uhile ono unites with the gcrm-ecll, the other fuses with the two polar " 
nuclei, which unite together to give rise to the endosperm.* 
Teleological Deductions. — When the fact was thoroughly gi asped 
that the stamens were male structures, and the pistil female, then it was 
thought that these organs gave good illustrations for teleology, that in 
flowers with pendulous stamens, the stigma hung below these, so that the 
pollen could fall upon it, as in Fuchsias ; hut that an erect flower had 
a shorter style, so as to keep the anthers still above the stigma, as in the 
Crocus. It did not seem to occur to these observers (even including 
Linn;eus) that it would be wiser to put the anthers against or in close 
contact with the stigma in every case to avoid all chance of loss. Nor is 
it true, for in the pin-eyed Primroses the stamens are below the stigma. 
jMoreover, in the majority of conspicuous flowers the anthers are mature 
before the pistil, which remain unreceptive until all the pollen is shed. 
In those days it was thought that every flower which contained both 
stamens and pistil was thus arranged to fertilise itself. 
Methods of Pollination.— One of the first botanists to observe the 
correlations between the structure of flowers and insects which visited 
them for honey or pollen was 8prengel,t who, as Darwin says, " clearly 
proved by innumerable observations how essential a part insects play in 
the fertilisation of many plants. But he was in advance of his age." ± 
It was not until Darwin's "Fertilisation of Orchids" appeared in 1862 
that botanists really became alive to the great importance of this 
subject. 
As now recognised, plants are seen to be pollinated in three ways, 
called respectively " self-fertilisation," when the pollen of the stamens is 
naturally applied to the stigmas of the same flower ; " insect-fertilisation," 
when it is carried from one flower to another ; and " wind- fertilisation," 
when the air takes the place of the insect. 
The question next arose as to what is the relative value of each of 
these three methods respectively. Darwin studied the subject experi- 
mentally, but in the main employed garden flow^ers of fair or considerable 
size, or at least conspicuous flowers. Now all these are naturally adapted 
to receive the visits of insects, and are, so to say, not only in the form of 
their flowers, but also physiologically adapted to be fertilised by foreign 
pollen rather than their own. 
The general result of his comparative experiments between cross and 
self- fertilisation gave the benefit to the former in height, Sec, and in 
fertility by seeding ; from which he deduced a supposed advantage in a 
plant being crossed, and he drew the opposite conclusion that " Nature 
abhors self -fertilisation." A careful analysis of his results, however, 
prove that when a plant is artificially self-fertilised for a few years {i.e. 
a plant usually visited by insects) the ratio of fertility steadily improves 
till it often beats that of the individuals regularly and artificially crossed 
every year. Secondly, Darwin fomid many of the plants he experimented 
upon, thou"gh specially adapted by the structure of the flowers to insect 
* Rcviic Gnu'rale dc liotaniquc, lo avril 1899, p. 129. The paper is entitled 
Sur les Antherozoitles ct la Doable Copulation Sexuelle chez les Vegetaux 
Angiospermes."' 
t Das entdeckte Gcheiinniss der Natur, 1793. 
J Cross- and Self-fertilisation of Plants, p. 5. 
