POLLINATION BY THE WIND 



95 



pistillate flowers. All of these flowers are visited by a little wasp 

 (Blastophaga grossorum). When it visits the short-styled and 

 staminate fig, it lays its eggs in the ovary, which it can easily reach 

 with its egg-depositing organ (the ovipositor) . The females which 

 hatch work their way out and in doing so brush against the stami- 

 nate flowers, thus collecting pollen on their bodies. They then 

 seek other figs in order to lay their eggs. If a wasp reaches another 

 short-styled flower cluster, the eggs are laid and development takes 

 place as before. But if it flies to a long-styled cluster, it cannot 

 reach the ovary to deposit its eggs. In both cases, however, the 

 wasp has carried pollen to the stigma and pollination takes place 

 with the subsequent development of seeds. The figs we eat are 

 developed from the long-styled pistillate flowers. By importing 

 the wasps to California it is possible to grow figs where for years 

 it was believed that the climate prevented them from ripening. 



Pollination by the wind. Not all flowers are dependent upon 

 insects for cross-pollination. Many of the earliest spring flowers 

 appear almost before the in- 

 sects do. In many trees, 

 such as the oak, poplar, and 

 maple, the flowers open be- 

 fore the leaves come out. 

 Such flowers are usually de- 

 pendent upon the wind to 

 carry the pollen from the 

 stamens of one flower to the 

 pistil of another. 



Among the adaptations 

 that a wind-pollinated flower 

 shows are : (1) The develop- 

 ment of many pollen grains to 

 each ovule. In flowers which 

 are pollinated by the wind, a 

 large number of the pollen 

 grains never reach their des- 

 tination and are wasted. Therefore thousands of 

 must be formed to every ovule produced. 



A wind-pollinated flower. What devices are shown 

 that aid in cross-pollination? 



pollen grains 



