446 THE RESULTS OF EVOLUTION 



other insects possess a color sense and are attracted by 

 flowers in consequence. 



It is also probable that odors attract insects. This is 

 certainly the case with several species of plants related 

 to the common skunk-cabbage, whose flowers possess a 

 strong odor of decaying meat and are pollinated by mul- 

 titudes of flesh-flies which crawl over them and even 

 deposit eggs. Needless to state, the instincts of the flies 

 in this case are faulty, since the young soon starve to 

 death, while the plant profits by the deception and pro- 

 duces seeds. 



In addition to alluring colors and scents there are 

 many mechanical adaptations in flowers which further 

 insure pollination. The nectar is usually located deep 

 within the flower, so that to reach it the insect must 

 inevitably brush against the pollen. In the Dutchman's 

 pipe and related plants, there are inwardly directed hairs 

 which prevent the escape of the visiting flies until they 

 have coated themselves with pollen. With the withering 

 of the hairs the captives escape to another blossom. The 

 flowers of the sage are so adapted that the stamens are 

 caused by the entering insect to bend down and dab a 

 mass of pollen on its back. In the orchids, adaptations 

 of this class reach a high degree of development. In 

 addition to attractively colored footpaths up which the 

 insect is invited to walk, there are delicately adjusted 

 contrivances for attaching pollen to the visitor or for 

 actually discharging it at its head. The details of the 

 process, along with many other examples, are given in 

 Darwin's work on the " Fertilization of Orchids." 



