HOW PLANTS ARE PROPAGATED 



93 



In some flowers the pollen can fall upon the stigma 

 of the same flower and 

 make good seed (self- 

 pollination) ; in others it 

 cannot, and the insects 

 or the wind usually bring 

 pollen from other flowers 

 (cross-pollination) . 



What flowers can set 

 seed without the help of 

 insects or wind? Experi- 

 ment on such plants as 

 you can. Tie paper bags 

 over the buds before they 

 open, as shown in figure 

 49. If they set seed, we 

 know that they do not 

 need the aid of wind or 

 insects ; but with such 

 aid they make better 

 seed than without it, for 

 the pollen from another 

 flower makes better seed 

 than pollen from the 

 same flower. 



Insects bring pollen to 

 some flowers. We are told that insects are attracted 

 by the bright colors of the petals, which are like sign- 



FIG. 49. A paper bag tied over a 

 flower to keep out pollen. 



