section_path: Seed dissemination
section_name: Seed dissemination
paragraph_text: Seed dissemination
  
  Variations in fruit structures largely depend on the modes of dispersal applied to their seeds. Dispersal is achieved by wind or water, by explosive dehiscence, and by interactions with animals.
  
  Some fruits present their outer skins or shells coated with spikes or hooked burrs; these evolved either to deter would-be foragers from feeding on them or to serve to attach themselves to the hair, feathers, legs, or clothing of animals, thereby using them as dispersal agents. These plants are termed zoochorous; common examples include cocklebur, unicorn plant, and beggarticks (or Spanish needle).
  
  By developments of mutual evolution, the fleshy produce of fruits typically appeals to hungry animals, such that the seeds contained within are taken in, carried away, and later deposited (i.e., defecated) at a distance from the parent plant. Likewise, the nutritious, oily kernels of nuts typically motivate birds and squirrels to hoard them, burying them in soil to retrieve later during the winter of scarcity; thereby, uneaten seeds are sown effectively under natural conditions to germinate and grow a new plant some distance away from the parent.
  
  Other fruits have evolved flattened and elongated wings or helicopter-like blades, e.g., elm, maple, and tuliptree. This mechanism increases dispersal distance away from the parent via wind. Other wind-dispersed fruit have tiny " parachutes ", e.g., dandelion, milkweed, salsify.
  
  Coconut fruits can float thousands of miles in the ocean, thereby spreading their seeds. Other fruits that can disperse via water are nipa palm and screw pine.
  
  Some fruits have evolved propulsive mechanisms that fling seeds substantial distances – perhaps up to 100 m (330 ft) in the case of the sandbox tree – via explosive dehiscence or other such mechanisms (see impatiens and squirting cucumber).