The Angiosperms 179 



culiar mouth-parts of the flower-haunting insects, 

 like the bees and butterflies, unquestionably owe their 

 existence to the peculiar structures of the flowers 

 they visit, and the flowers become adapted to the 

 associated structures of the insects. The enor- 

 mously long proboscides of the big hawk-moths are 

 only to be explained as organs especially fitted for 

 probing the deep nectaries of certain flowers, and 

 the pollen-receptacles of the bee must have been de- 

 veloped in connection with the habit of collecting 

 pollen for food. It has often been claimed that the 

 peculiar formation of many flowers is the direct 

 reaction to stimuli, due to the irritation of special 

 parts of the flower during the visits of insects. It 

 may be said, however, that this view is not generally 

 accepted. 



Birds as Agents in Pollination. Many flowers 

 are adapted to fertilization by birds, which have be- 

 come modified accordingly. The great American 

 family of humming-birds, and the honey-suckers of 

 the Old World, are the best-known types. These 

 two groups of birds, although not at all related, 

 show curiously similar characters in size, color, and 

 form, and the flowers they frequent, both in shape 

 and color, show a corresponding similarity. Bright 

 red seems to be the favorite color of these much fre- 

 quented flowers, and in America many vivid red 

 flowers, like the trumpet-creeper, the scarlet balm, 

 scarlet sage, trumpet honeysuckle, and many 

 others may be mentioned as special favorites of 



