POLLINATION AND FERTILIZATION 



143 



maturing, close over the stigmas and insure self-pollination. 

 The fact that seeds are abundantly produced shows that 



the pollination is 

 effective. 



136. Corn; pol- 

 lination by wind. 

 Indian corn af- 

 fords an admirable 

 example of polli- 

 nation effected by 

 aid of the wind. 

 The pollen is pro- 

 duced in the staminate flower 

 clusters, which are commonly 

 known as the tassel (fig. 1 26), 

 borne at the summit of the 

 cornstalk. Each cluster con- 

 sists of many stamens, and every stamen 

 produces a multitude of dry, dust-like pol- 

 len grains, which are carried for long dis- 

 tances by the wind. The familiar corn silk, 

 which protrudes from inside the husk of 

 the young ear of corn, is composed of 

 many thread-like styles (one from each 

 grain of corn). The styles terminate in a 

 two-forked, hairy stigma (fig. 127 C, st). 

 The brush-like character of the protruding 

 stigmas makes them very efficient in catch- 

 ing flying pollen grains. 



If the pollen from a corn plant is shaken 

 down upon the stigmas of. the same plant, 

 self-pollination only is effected and poor seed results. If the 

 pollen which pollinates an ear comes from another corn plant, 

 cross-pollination is effected and good seed results. Figure 159 

 shows the difference in growth between plants produced in 

 the next generation from the two kinds of seed. 



FIG. 126. Part of a 

 corn tassel (stami- 

 nate flower cluster) 



br, a bract; st, stamens. 

 One half natural size 



