THE WOKK OF FTjOWEBS 



291 



place, the eg^ does not 

 ordinarily develop; 

 hence we see why 

 pollen is necessary in 

 order to set seed. If 

 we examine various 

 flowers with a hand- 

 lens, we find the pol- 

 len deposited in a par- 

 ticular spot, which is 

 provided with brushes, 

 hairs or sticky sub- 

 stances in order to 

 retain it. This spot is 

 called the stigma (see 

 Fig. 161). What hap- 

 pens if we remove the 

 stigma ? Remove the 

 stigma before the bud 

 is open, being careful 

 not to injure the other 

 parts of the flower. 

 Do not protect the 

 flowers from insects, 

 but rather assist pol- 

 lination by placing 

 pollen on the flower. 

 Do you find that flow- 



1G4. Embryo s;ic of ;i Lily, showing the iinion of 

 the nucleus from the pollen-tube {pn) with the 

 egg(e): the second pollen -tvibe nu<-leus (spn) 

 xmites with two endosperm pro nuclei {nid), 

 which nniltiply and form the endosperm: {ant) 

 antipodal cells, (nr) nurse nuclei which help 

 nurish the egg, etc., {p) pollen-tube. 



