Then, again, there is the flower of the nettle, which in most plants is so much the most conspicuous part of all. Yet in this particular plant it is so unobtrusive that most people never notice its existence in any way. That is because the nettle is wind-fertilized, and so does not need bright and attractive petals. Here are the flowering branches, a lot of little forked antler-like spikes, sticking out at right angles from the stem, and half concealed by the leaves of the row above them. Like many other wind-fertilized flowers, the stamens and pistils are collected on different plants--a plan which absolutely insures cross-fertilization, without the aid of the insects. I pick one of the stamen-bearing clusters, and can see that it is made up of small separate green blossoms, each with four tiny leaf-like petals, and with four stamens doubled up in the center. I touch the flowers with the tip of my pocket knife, and in a second the four stamens jump out elastically as if alive, and dust the white pollen all over my fingers. Why should they act like this? Such tricks are not uncommon in bee-fertilized flowers, because they insure the pollen being shed only when a bee thrusts his head into the blossom; but what use can this device be to the wind-fertilized nettle? I think the object is somewhat after this fashion. If the pollen were shed during perfectly calm weather, it would simply fall upon the ground, without reaching the pistils of neighboring plants at all. But by having the stamens thus doubled up, with elastic stalks, it happens that even when ripe they do not open and shed the pollen unless upon the occurrence of some slight concussion. This concussion is given when the stems are waved about by the wind; and then the pollen is shaken out under circumstances which give it the best chance of reaching the pistil.