Early land plants faced a number of challenges when they began to colonize terrestrial territories, such as evolving ways to support themselves and prevent desiccation, according to documentation on The University of the West Indies. Additionally, plants had to evolve new methods for spore dispersal and egg fertilization if they were to survive out of the water. Overcoming these challenges led to many of the unique adaptations of modern plants.
The first plants evolved in ecosystems that were suspended in water. Accordingly, they relied on this constant resource for survival. Primitive plants used the water to disperse their spores and as a medium through which sperm cells could swim to egg cells. Incidentally, the water helped to support the plants and keep them hydrated. The evolution of vascular systems helped plants to transport water throughout their structures and to remain stable by using the pressure created by the water for support. To overcome the difficulties of spore dispersal, plants evolved many different types of spores that travel better in the air. Modern plants have evolved a number of methods of transporting sperm cells, including insects, wind and birds.
Some land plants, such as mosses, still rely on water for egg fertilization. Their sperm cells must swim through water to reach the egg cells. This is one of the reasons that moss is always found in damp areas.