Seed dispersal occurs by the following agencies :
(a)Dispersal by animals -
1. Birds and animals can eat the fruits and excrete the seeds away from the parent plant.
2. Some seeds have barbs or other structures that get attached to the animal's body and are carried to new sites.
3. Some seeds have spine-like structures on them.
4. They get stuck to the fur of animals and thus get spread to different places. Examples; Beggar tick, Xanthium, etc.
(b)Dispersal by the wind -
1. Seeds that get dispersed by wind are usually smaller in size or they have wings or hair-like structures.
2. For example, winged seeds of drumsticks, hairy fruit of the sunflower, etc. are dispersed by wind.
(c)Dispersal by water -
Many aquatic plants or plants that live near water have seeds that can float and are carried away by water. For example, coconuts can float and are dispersed by water.
(d) Dispersal by an explosion -
1. Sometimes the seeds are dispersed by the bursting of fruits with sudden jerks. The seeds get scattered or distributed far from the parent plant.
2. Examples of such plants are castor and balsam.
(e)Dispersal by humans -
Human beings also help in the dispersal of seeds, especially during farming.