FLOWERS AND THEIR WORK 



49 



Condition of st;inu'ns and pistils in tlic spiked loose- 

 strife (Lythrum salicaria). 



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

 in one flower, and long sf \les witli short or kiw-plaeed filaments in 

 the other. Pollination will he elfet'ted 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 ha^e 

 this peculiar condition 

 are said to hediinorphic 

 (Greek = of two forms) . 

 There are, as in the 

 case of the loosestrife, 

 trimorphic flowers 

 having pistils and 

 stamens of three 

 lengths. 



Charles Darwin, who 

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

 "^^'henbeessuck the flowers, the anthers of the longest stamens . . . 

 are rubbed against the abdomen and inner sides of the bind 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 tlie stamens to the pistil of corresponding 

 length." 1 



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

 by tlie \nnd, insects, or other agencies, must be dry. In some 

 flowers the irregular form of the corolla protects the pollen from 

 dampness. Other flowers ckxe 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 



' Forma of Flowers, page 159. 

 HUNT. E8. BIO. 4 



