PERFECT FLOWERS 



55 



ried down to the short stigmas. But, in the latter 

 case, in passing down the long tube, some of the 

 fine pollen may easily lodge upon a long stigma. 

 What then will happen? Nothing! For the long 

 pistils are sensitive to the coarse pollen only, and 

 cannot be fertilised by the finer. Hence, the long- 

 stamen flowers fertilise those with short stamens, 

 and vice versa. 



The Houstonia is fertilised by the bees, Halictus 

 and Andrena, and by the smaller butterflies, es- 



HOUSTONIA 



pecially the clouded sulphur (Coleas philodice), 

 the meadow fritillary (Brenthis bellona) and the 

 painted lady (Pyrameis Cardui). Flowers such 

 as those of the Houstonia are called dimorphic, or 

 "two-formed." Another example is: 



GARDEN GERANIUM 



As a study in dimorphism, the garden geranium 

 is most valuable, as it is easy to obtain, and its parts 



