CHAPTER XVII 

 ECOLOGY OF FLOWERS; POLLINATION 



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

 concerned mainly with the means by which the transfer- 

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

 in which pollen is kept away from undesirable insect 

 visitors and from rain. 



197. 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. At present it is 

 known that probably nearly all attractive flowers, even if 

 they can produce some seed when self-pollinated, do far 

 better when pollinated from the flowers of another plant 

 of the same kind.i 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 treated with pollen 

 from another flower of the same kind, or cross-pollinated? 



198. Wind-Pollinated Flowers.s — It has already been 

 mentioned that some pollen is dry and powdery and other 

 kinds are more or less sticky. Pollen of the dusty sort is 

 light, and therefore adapted to be blown about by the 



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

 (especially Chapters I and II). 



2 On dispersion of pollen see Kerner and Oliver, Vol. II, pp. 129-287. 

 8 See Newell's Reader in Botany, Part II, Chapter VII. 



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