Wind carried fruits and seeds that are heavier need a ‘sail’. The hairs on the Dandelion fruit or the fluffy strands of the Wild Clematis fruit (Old Man’s Beard) create wind resistance, enabling the breeze to lift and transport the fruits to new locations.
For trees, shedding their fruits from high up, all that is necessary is a way of delaying the fall long enough for the wind to carry them some distance from the parent. An outgrowth of the fruit wall, and a seed asymmetrically placed inside makes the fruits of Sycamore, Field Maple and Ash spin as they fall, generating lift that delays descent long enough for the landing to be some way from the parent.
If the plants are growing closer to the ground, hitching a lift on the fur of ground moving animals becomes an effective strategy. The burrs from Burdock (left) that can be a nuisance in the animals’ fur have an unseen sophistication in the way they operate. The hooked fruits are obvious enough, but initially a dog will largely ignore them, since they cause little irritation. Later though, as the burr dries out, small straight sharp fibres are released. These work their way through to the animal’s skin and set it scratching a day or so after the burr was picked up.
Wood Avens (Geum urbanum - right) have styles with an odd kink in. When the fruits mature these break off half way along the kink, leaving a very effective hook, for animal dispersal.
Some plants like vetches and other members of the Fabaceae (pea family) have pods which, unlike peas and beans, dry out to tough leathery husks. As the pod dries, fibres in the fruit wall shrink, tending to twist each half of the pod in opposite directions. For a while the tissue holding the sides together withstands the strain, but at some point the tension becomes too much and it breaks. The explosive curling of each side of the pod whips the small cannonball-like seed out, throwing them some distance from the parent.