Page:Popular Science Monthly Volume 5.djvu/147

Rh tentacle. With this she collects the pollen and thrusts it into the stigmatic 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.



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