Vascular plants are classified as higher plants, as opposed to non-vascular plants. They evolved approximately 410 million years ago and now are the dominant plant form. Vascular plants have several characteristics that set them apart from non-vascular plants.
All vascular plants are differentiated from non-vascular plants in that they contain roots, stems, leaves and an internal vascular network. The root system takes in water and nutrients from the soil, while the shoot system, made up of stems and leaves, specializes in photosynthesis. The vascular network is made up of conducting tissues referred to as xylem and phloem. Xylem carries water and nutrients upward from the roots, while phloem carries the products of photosynthesis to all parts of the plant as needed.
All vascular plants reproduce using either seeds or spores. They are all oogamous (having a larger female gamete or egg, and a smaller motile male gamete or sperm). Haploid cells (the male and female sperm and egg) each carry half the genetic material of the parent and unite to form a zygote with the full complement of chromosomes.
Xylem tracheary elements have rigid walls containing cellulose. When the tracheids die, their walls persist and serve as a support structure. A good example of this is the wood of trees. The presence of cellulose allows the plant to grow upright, producing more leaves for photosynthesis. Non-vascular plants are limited to one or two centimeters in height.