CHAPTER XXVIli 

 ECOLOGY OF FLOWERS 



422. Topics of the Chapter. — The ecology of flowers is 

 concerned mainly with the means by which the transfer- 

 ence of pollen or pollinMion is effected, and with the ways 

 in which pollen is kept away from undesirable insect 

 visitors and from rain. 



423. Cross-Pollination and Self-PoUination. — It was 

 long supposed by botanists that the pollen of any perfect 

 flower needed only to be placed on the stigma of the same 

 flower to insure satisfactory fertilization. IBut in 1857 

 and 1858 the great English naturalist, Charles Darwin, 

 stated that certain kinds of flowers were entirely dependent 

 for fertilization on the transference of pollen from one 

 plant to another, and he and other botanists soon extended 

 the list of such flowers until it came to include most of 

 the showy, sweet-scented, or otherwise conspicuous kinds. 

 It was also shown that probably nearly all attractive 

 flowers, even if they can produce some seed when self- 

 poUinated, do far better when pollinated from the flowers 

 of another plant of the ' same kind.^ This important fact 

 was established by a long series of experiments on the 

 number and vitality of seeds produced by a flower when 

 treated with its own pollen, or self-pollinated, and when 



1 See Darwin's Cross and Self-Fertilization in the Vegetable Kingdom 

 (especially Chapters I and H). 



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