CROSS-POLLINATION 165 



perfect flowers, even if they have both calyx and corolla. 

 The pear blossom that was described above was a perfect 

 flower ; each kind of cornflower is imperfect. 



115. Cross-pollination. Even in some kinds of perfect 

 flowers the pistil often gets its pollen from the stamen of an- 

 other flower instead of from its own stamen. All clover 

 blossoms have both stamen and pistil ; but the pollen and 

 ovules of the same blossom do not readily unite. The 



EFFECT OF POOR POLLINATION. 



pistil uses pollen brought to it from another blossom. 

 This is cross-pollination. 



With farm plants, cross-pollination is far more common 

 than self-pollination. Nature seems to have found out 

 that cross-pollination gives more vigorous plants. Charles 

 Darwin, one of the world's greatest scientists, proved by 

 experiments that when cabbage flowers used their own 

 pollen, they grew heads only a fourth as heavy as when 

 they used pollen from another cabbage. 



116. In cross-pollination how is the pollen carried from plant 

 to plant? The wind carries corn pollen. Most of it falls 

 on the ground or on other plants ; but each stalk pro- 

 duces a large amount, and its high place on the plant 

 helps the wind to distribute it well, so as to powder nearly 

 every bunch of corn silk with it. 1 



1 If the corn silk receives pollen from the tassel of its own stalk, the polli- 

 nation is not cross-pollination, because both flowers belong to the same plant. 

 Corn uses both self-pollination and cross-pollination. 



