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-Pollination.—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! 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.3— 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 
1See 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. 
3 See Newell’s Reader in Botany, Part Il, Chapter VII. 
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