FLOWERS AND THEIR WORK 



49 



lengths. 



Charles Darwin,who 



flowers. Short styles and long or high-placed filaments are found 

 in one flower, and long styles with short or low-placed filaments in 

 the other. Pollination will be effected only when some of the 

 pollen from a low-placed anther reaches the stigma of a short- 

 styled flower, or when the pollen from a high anther is placed upon 

 a long-styled pistil. 

 Flowers which have 

 this peculiar condition 

 are said to be dimorphic 

 (Greek = of two forms) . 

 There are, as in the 

 case of the loosestrife, 

 trimorphic flowers 

 having pistils and 

 stamens of three 



Condition of stamens and pistils in the spiked loose- 

 strife (Ly thrum salicaria). 



worked out the fertilization of this flower, describes it as follows : 

 " When bees suck the flowers, the anthers of the longest stamens . . . 

 are rubbed against the abdomen and inner sides of the hind legs 

 as is likewise the stigma of the long-styled form (see diagram). 

 The anthers of the midlength stamens and the stigma of the 

 midstyled form are rubbed against the upper side of the thorax 

 and between the front pair of legs. And, lastly, the anther of 

 the shortest stamens and the stigma of the short-styled form are 

 rubbed against the proboscis and the chin; for the bees in suck- 

 ing the flowers insert only the front part of the head into the 

 flower. ... It follows that insects will generally carry the pollen 

 of each form from the stamens to the pistil of corresponding 

 length." l 



Protection of Pollen. Pollen, in order to be carried effectively 

 by the wind, bisects, or other agencies, must be dry. In some 

 flowers the irregular form of the corolla protects the pollen from 

 dampness. Other flowers close up at night, as the morning-glory 

 and four-o'clock. Still others, as the bellflower, droop during a 

 shower or at night. 



Pollen is also protected from insect visitors which would carry 



1 Forms of Flowers, page 159. 

 HUNT. ES. BIO. 4 



