POLLINATION AND FERTILIZATION 



119 



the social relations between plants and other injurious or help- 

 ful plants and animals. 1 



The ecology of flowers is largely concerned with the ways in 

 which pollination is brought about. 2 This subject is of suffi- 

 cient importance to have accumulated an 

 extensive literature, the principal treatise 

 upon it being Knuth's "Bliithenbiologie," em- 

 bracing nearly three thousand pages. There 

 is also an excellent English translation of 

 this remarkable book. 3 



111. Pollination and floral characteristics. 

 Some of the most obvious divisions of flowers 

 into everyday groups, such as are made by 

 children and other unscientific people, are 

 those into scented and scentless, showy and 

 inconspicuous kinds. Another less obvious 

 but important distinction is based on the 

 presence or absence of the sweet liquid (com- 

 monly called honey, but more properly known 

 as nectar) so familiar at the tips of colum- 

 bine spurs and in clover and honeysuckle 

 blossoms. Such characteristics as those just 

 mentioned have much to do with the way in 

 which flowers have their pollen transferred 

 from anthers to stigma. 



Flowers with feathery stigmas (Fig. 110) 

 and dry, dust-like pollen are usually polli- 

 nated by the wind. 



Flowers with stigmas which, before they wither, curve so 

 as to bring the anthers into contact with the stigma (Fig. Ill) 

 are usually self -pollinated. 



1 A great deal of what was said about the behavior of roots, stems, and 

 leaves in Chapters III-VI is to be classed as plant ecology, though it was 

 not given a separate name in those chapters. 



2 See Kerner-Oliver, Natural History of Plants, Vol. II. Henry Holt and 

 Company, New York. 



8 Knuth-Davis, Handbook of Flower Pollination. Clarendon Press, Oxford. 



FIG. 110. Pistil of 

 timothy with feath- 

 ery stigmas 



sti, stigmas. Mag- 

 nified about twenty 

 times 



