Vascular plants
Division Tracheophyta

Tracheophytes are vascular plants. All have two kinds of special tissues for moving nutrients and water called xylem and phloem. Xylem tissue cells carry water from the roots to the leaves. Phloem tissue cells carry sugars made during photosynthesis in the leaves to other parts of the plant.

Subdivision Lycophytina
These plants, which include club mosses, iseotopsids, and selaginellas, have leaves with only one, central, vein. Spores are produced in sporangia that grow in the stem-leaf nodes or on the leaves. The sporangia are kidney shaped.

Class Lycopodiopsida: Lycopodiopsids are the club mosses and ground pines. Many species have stems that produce needlelike leaves. Spores are often tightly clustered at the tips of branches.

Class Selaginellopsida: Selaginellas produce separate male and female spores. They are leafy and usually delicate in construction. Though most selaginellas live in moist places, one species named the "resurrection plant" occurs in the desert.

Class Isoetopsida: Isoetopsids produce two kinds of spores, one male and one female. These small plants have grasslike leaves and live in wet places. About 360 million years ago, some isoetopsids were large trees.

Subdivision Euphyllophytina Euphyllophytes include most of the vascular plants. Their leaves usually have many veins and their reproductive organs and internal structures are different from those of the Lycophytina plants.

Class Psilopsida: The plants in this class are called whisk ferns or fork ferns. They have many slender, highly branched aerial stems by which the plants spread. They reproduce from spores. These are rare plants and can be found in tropical and subtropical regions.

Class Sphenopsida: Living sphenopsids are known as horsetails or scouring rushes. Stems are hollow except at the nodes, giving them a jointed appearance. They grow 2 to 3 feet (61 to 91 centimeters) tall and reproduce by means of spores.

Class Pteridopsida: This class includes the ferns. Most ferns have large leaves called fronds which are usually made up of smaller leaflets. They reproduce by means of spores. Ferns are commonly seen on forest floors, but tropical fern trees may grow more than 65 feet (20 meters) high. Next to flowering plants, ferns are the most diverse group of plants in the division Tracheophyta.

Class Gymnospermopsida: Gymnosperms reproduce by means of naked, or uncovered, seeds. Many gymnosperms are evergreens with a wide variety of leaf structures. Conifers, cycads, ginkgoes, and gnetaleans are in this class.

Order Coniferales: Most conifers are evergreen trees or shrubs with needlelike or scalelike leaves and most conifers bear their seeds in woody cones.

Order Cycadales: Cycads grow fern or palmlike leaves. Their seeds are borne in large cones. Many species have unbranched, erect stems, while others have partially underground stems called tubers. Some cycads are trees.

Order Ginkgoales: Ginkgoes are easily recognized by their fan-shaped leaves. They bear fleshy seeds at the end of short branches. Only one species of ginkgo exists today.

Order Gnetales: Gnetaleans are closely related to flowering plants. Gnetalean seeds are borne in complex cones. They vary widely in appearance and and typically live in deserts and tropical rain forests.

Class Anthopsida: Flowering plants, or angiosperms, make up this class. All angiosperms reproduce by means of covered seeds. Once fertilization, the ovary grows into a fruit that encloses the seeds. Angiosperms, the most diverse group of plants can be found growing from the tropics to the polar regions and are divided into two subclasses, Monocotyledonae and Dicotyledonae.

Subclass Monocotyledonae: Monocots have seeds with only one cotyledon (seed leaf). The main veins in the leaves of these plants usually run parallel to each other and usually occur in multiples of three.

Subclass Dicotyledonae: Dicots have seeds with two cotyledons. Their leaves have a complex system of veins. The dicot's flower parts usually occur in multiples of four, sometimes five.

Nonvascular plants
Division Bryophyta

Mosses, liverworts, hornworts make up this division of plants. These plants reproduce by means of spores and lack true leaves, stems, or roots. Most live in moist areas. However, some mosses can withstand severe temperatures and are found in Arctic or desert regions.

Class Musci: True mosses make up this class. Stems may be erect or horizontal and bear many leaflike growths. Rarely do they grow over 8 inches (20 centimeters) long.

Class Hepaticae: Liverworts make up this class. These small plants may be flat and ribbon-shaped or leafy. Their growth habit keeps them low to the ground.

Class Anthocerotae: Hornworts usually grow only 3/8 to 3/4 inch (1 to 2 centimeters) wide. The gametophyte is ribbonlike in appearnce.