Seeds vary widely in size and shape. Some of the largest seeds come from trees, but the largest tree, the Giant sequoia (Sequoiadendron giganteum), produces some of the smallest tree seeds.
In order to disperse seeds, they are often equipped with features that facilitate wind dispersal, such as wings (birch, ash, maple).
Seeds are also dispersed by animals, thanks to their edible fruits. Seeds of conifers (the largest group of gymnosperms) are embedded in the cone. Sometimes the seeds are trapped in the cones for many years, waiting for an event to release them. Such an event is sometimes fire, which stimulates the release and germination of pine seeds while enriching the soil with wood ash and removing competing vegetation. Many angiosperms (including Acacia cyclops and Acacia mangium) have seeds whose germination is also stimulated by high temperatures.
