"Blossom Hosts and Insect Guests 



The purple loosestrife, Lythrinn Salicaria, pro- 

 duces flowers whose stamens and pistils occur in 

 three different lengths. In this species only pollen 

 from the longest stamens can fully fertilize the 

 longest pistils ; only that from the shortest stamens 

 the shortest pistils, and only that from the medium- 

 length stamens the medium-length pistils. 



The common wood-sorrel and the blue pickerel 

 weed also produce trimorphic or three-formed 

 flowers. 





66 



