PEBTILIZATION. 161 



ears or none at all. The common ragweed, another monoecious 

 plant, is remarkable for the great quantities of pollen which 

 shake off it on to the shoes or clothes of the passer-by, and it 

 is wind-fertilized. So, too, are the monoecious pines, and 

 these produce so much pollen that it has been mistaken for 

 showers of sulphur, falling often at long distances from the 

 woods where it was produced. The pistil of wind-fertilized 

 flowers is often feathery and thus adapted to catch flying 

 pollen-grains'(Fig. 143). Other char- 

 acteristics of such flowers are the 

 inconspicuous character of their flow- 

 ers, which are usually green or green- 

 ish, the absence of odor and of 

 nectar, the regularity of the corolla, fig. 143.— pistiiof aGrass. 



and the appearance of the flowers «. ovary ; 6, feathery stigma, 

 , « JIT , T ■ adapted for wind-f ertiliza- 



betore the leaves or their occurrence tion. 

 on stalks raised above the leaves. 



Pollen is, in the case of a few aquatic plants, carried from 

 flower to flower by the water on which it floats. 



198. Insect- Fertilized Flowers. — Most plants which require 

 cross-fertilization depend upon insects as pollen-carriers,^ and 

 it may be stated as a general fact that the showy colors and 

 markings of flowers and their odors, all serve as so many 

 advertisements of the nectar (commonly but wrongly called 

 honey), or of the nourishing pollen which the flower has to 

 offer to insect-visitors. 



Many insects depend mainly or wholly upon the nectar and 

 the pollen of flowers for their food. Such insects usually 

 visit during the day only one kind of flower, and therefore 

 carry but one kind of pollen. Going straight from one flower 

 to another with this, they evidently waste far less pollen than 

 the wind or water must waste. It is therefore clearly 

 advantageous to flowers to develop such adaptations as fit 



1 A few are fertilized by snails ; many more by hununing-birds and other birds. 



