THE DISPERSAL OF SEEDS 299 



The pollen used to fertilize a flower may come from the stamens of 

 the same flower, or from other flowers near or far away. The air is 

 often full of pollen grains. Many plants do not depend on chance for 

 fertilization, but develop structures that attract insects or birds. 

 These creatures then carry the pollen from flower to flower. Thus it 

 comes about that many flowers have a bright color and a sweet odor, 

 which tell the insect where food is to be found. For some creatures, 

 such as butterflies, the flower secretes a sweet liquid, called nectar. 

 Bees feed upon the pollen itself. The nectar is usually stored at a 

 place beyond the organs of reproduction, so that the visiting insect 

 must brush against these organs. The insect thus becomes loaded 

 with the pollen grains of one flower, and brushes them against the 

 stigma of the next flower it visits. 



320. The Dispersal of Seeds. The parent plant is 

 usually not through with its labors when it has produced 

 the seed; most plants have worked out a method by 

 which the seed shall be carried away to new 

 places to grow. These plant devices are 

 often very successful. In some plants, as in 

 violets, the seed pod bursts open with con- 

 siderable force, scattering the seed to a dis- 

 tance. The seed pod itself is often arranged 

 so that it can be carried off by the air. Ex- 

 amples are the winged seeds of the maple 

 (Fig. 245), and the tufted seeds of the dan- 

 delion and thistle. Multitudes of seeds are 

 carried about by currents of water, even by those of 

 the ocean itself. Seeds like the "stickers' 7 of the cockle- 

 bur and burdock are carried about by animals to a new 

 place for germination. 



Fruits, which are the ripened ovaries or, sometimes, 

 other parts of the organs of reproduction, are also devices 



