8 



GENERAL BIOLOGY 



that are generally located within the flower, and pollen is 

 the product of the stamens. In return for these the in- 

 sects serve the flowers by transferring the pollen of one 

 flower to the stigma of another, securing cross fertiliza- 

 tion. 



FIG 2. A bee (Macropis ciliatd) gathering pollen from 

 the erect stamens of a loosestrife flower (Steironema 

 ciliatum.) 



Figure 2 illustrates this relation. The yellow flowers 

 of the fringed loosestrife are not nectar-bearing but they 

 produce abundant pollen. This is much sought for by a 

 little black bee. The bee settles upon the tops of the clus- 

 tered and protruding stamens, as shown in the figure, and 

 scrapes the pollen out of the pollen cavities of the five long 

 curved anthers. In doing this it turns around several 

 times and gets the hair of its legs and of the under surface 

 of its body filled with closely packed pollen grains. It 

 visits a number of flowers in succession, and is very likely 

 to deposit upon the stigma of each one, some pollen 

 from another flower. 



It must be borne in mind that the purpose of the 

 flower is to produce seed. Seeds are ripened ovules: ovules 

 are contained in the ovule case, which is the swollen 



