THE CYCLE OF LIFE : FLOWERS 



49 



up the structure and activities of the various insects that visit 

 the flowers. While it is true that in order to be alive the activi- 

 ties of an organism must fit the surrounding conditions, it would 

 be a mistake to suppose that every structure and every character 

 and every activity is of value in keeping the organism alive. 

 There are many plants that have colored corollas (some kinds 

 of beans, for exam- 

 ple) but that do 

 not depend upon 

 insect visitors at 

 all, and there are 

 other plants that 

 receive insect visi- 

 tors without being 

 particularly showy. 

 Again, while there 

 are many insects 

 that help in pollen- 

 ation when they 

 come for nectar, 

 there are certain 

 plants that yield 

 nectar without get- 

 ting 



Fig. 2 2. Pollenation by birds 



The saber-billed humming bird visits certain large 

 flowers and laps up the sugary fluid, or nectar, and so 

 rubs off some of the pollen. When it visits another 

 flower, this pollen comes off onto the stigma. Certain 

 tropical flowers are said to be pollenated by bats that 

 come to them for nectar. (From an exhibit in the 

 American Museum of Natural History, New York) 



any use from 

 the visits of the in- 

 sects. For example, 

 nectar is sometimes 

 formed on the stems 

 and leaves of vari- 

 ous plants, including ferns (which produce no seeds at all). 

 40. Interdependence. In some cases the dependence between 

 insects and flowers is so great that it has an important bearing 

 on the practice of plant raisers. A poor supply of blossoms may 

 mean a poor honey crop and fewer bees the following season. 

 The lack of bees to pollenate the blossoms may mean a poor 

 fruit crop. 



