Four Main Groups of Plants

Mosses

• The moss group also includes plants like liverworts and hornworts. These plants grow in moist areas because they have no roots, stems or leaves to absorb water and must get water from their immediate surroundings. They don't have a vascular system like other plants. The root-like structures (called rhizoids) that sometimes emerge from the bottom of mosses may absorb a little water, but they mostly provide structure and the ability to adhere to rocks, soil, or other plants. Mosses are important because they often are the first plants to colonize an area, making way for other plants. Interestingly, many mosses and moss allies can become completely desiccated -- a condition that normally kills other plants -- and come back to life when rehydrated,

Ferns

• The fern group also includes the fern allies such as horsetails, club mosses and whisk ferns. These plants possess vascular systems, unlike the mosses, but they do not produce flowers or seeds like the angiosperms. They can achieve greater size because they are not completely dependent on environmental moisture, they can get moisture transported to their leaves from the roots. Ferns reproduce through spores rather than seeds, and reproduction happens in two steps. First, from the spores a tiny plant-like structure is produced, which in turn produces the sperm and egg needed for the more familiar secondary form often seen on forest floor. Ferns are environmentally important because they prevent soil erosion. They are economically important because they are grown in the nursery trade as both landscape plants and houseplants.

Conifers

• The conifers are also called gymnosperms. They create seeds, unlike mosses or ferns, but do not produce flowers. They have vascular systems that allow them to achieve great size, sometimes more than 100 feet in height. Unlike ferns, the seeds produced by gymnosperms contain all the needed parts to reproduce; they simply need to land in a favorable environment and they will sprout and grow without further need for pollination. Most gymnosperm seeds develop within a cone-like structure, and are not covered by an ovary (they are often called "naked" seeds). Gymnosperms are economically important as a source of lumber but also as a landscape plant.

Flowering Plants

• Flowering plants are called angiosperms. They have vascular systems, unlike mosses, but also produce flowers with an ovary covering the seeds, unlike gymnosperms of ferns. The flowers attract both animals and insects, enlisting their assistance in the pollination process. Some plants are not reliant on this process and simply disperse their pollen to the wind. The fleshy ovary protecting the seeds is a food source of both animals and humans, and assures that the seeds will be dispersed into locations away from the mother plant. Angiosperms are an important food source, but also economically important as landscape plants.