HAVE PLANTS A PEDIGREE f 



135 



tentacle. With this she collects the pollen and thrusts it into the stig- 

 matic tube against the stigma. In this pollen-mass she lays her eggs. 

 A single palpus of the female of a single species of moth, modified in a 

 peculiar way, is the means of perpetuating the yucca. In its native 

 home yucca and yuccasella are inseparable. In the north, yuccasella 

 does not thrive and yucca can set no seeds. 



Fig. 5. 



Well, if plants depend so much on insects, insects must have some 

 way of knowing where they are. As an optical instrument, the eye of 

 an insect is rather imperfect, but it is not color-blind. A butterfly 

 may not be sensitive to the harmonies of color, but it certainly knows 



