Microballistics in fungi and plants.

Ballistic movements in biology are powered by muscle contraction, explosive chemical reactions, the formation and collapse of gas bubbles, merger of fluid droplets, and release of hydrostatic pressure. At the macroscopic end of this kinetic carnival we find jumping fleas, violent spider jaws, shrimp claw hammers, and squirting beetles and cucumbers. The speeds are startling, but the mechanisms seem familiar because they occur on a spatial scale that overlaps with our physical experiences. We jump, albeit more slowly than fleas, for example, and it does not seem strange that seeds will spurt from a swollen cucumber when it hits the ground. Ballistics in microscopic dimensions are very different, operating in a seemingly alien world of fluid mechanics where thin air becomes soup and gravity vanishes.