152 Elementary Botany 



is a good example. There are six stamens surrounding the 

 pistil. If one is touched it springs forward towards the ovary. 

 At the base of the stamens are honey glands ; insects visiting the 

 flowers in search of honey strike against the stamens, causing 

 them to fall forward, scattering the pollen over the intruders' 

 bodies. 



In the Centaurea and some other Compositse the stamens 

 contract on touching. Some leaves, although they are not 

 sensitive to touch, close at the approach of night. The leaflets 

 of Wood-sorrel fold down, those of Clover fold up. Changes 

 of terhperature and variation in the amount of light produce 

 these movements. 



The opening and closing of flowers at certain hours of the 

 day is a phenomenon due to similar causes. 



