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Plant Classification List

(Kingdom Plantae)

In this table the name of the division of the plant kingdom is given first, followed in parenthesis by its more familiar classification.

Chlorophytacophyta (green algae) grow in fresh water and in seawater. More than 7,500 species are known. Their chloroplasts contain chlorophyll a and b, like most land plants the green algae are usually grass-green in color, and many species are unicellular. Most scientists believe that land plants originated from green algal ancestors.

Phacophycophyta (brown algae) are found mainly in ocean habitats. About 1,500 species are known. Their chloroplasts contain chlorophyll a and c and a brown pigment called xanthophylls, which gives these algae their dark color. Some of the brown algae, such as the giant kelp, may grow to enormous size. Cells within the brown algae known as seaweeds are often specialized for specific tasks.

Chrysophycophyta (yellow-green algae and golden, or golden-brown , algae) occur in fresh water and seawater. Over 6,00 species have been described. Like the brown algae, their chloroplasts contain chlorophyll a and c, and other pigments give these plants their characteristic yellowish color. The cell walls of these algae are compose of cellulose and silicon, which give them a glasslike appearance. Unlike other algae, the Chrysophycophyta do not store their food in the form of starch but in the form of oil or carbohydrates.

Rhodophycophyta (red algae) are abundant in ocean habitats, though a few species also occur in freshwater streams and lakes. About 3,900 species are known. Their chloroplasts contain chlorophyll  a and d a red pigment called phycocrythrin. These algae may grow at great depths in areas of the ocean where the water is clear. Some of them accumulate calcium carbonate and play a central role in the formation of limestone reefs.

Hepatophyta  (liverworts) are found in relatively moist habitats such as damp woods and along streams. The number of species exceeds 8,000. Liverworts have simple stems or no stems and may have simple leaves or flat green bodies that resemble leaves. They are the most primitive living land plants.

Anthocerotophyta (hornworts) occur in moist land habitats. There are fewer than 50 species. Although the hornworts resemble liverworts in general form, their reproductive structures are most similar to those of the mosses. For this reason, botanists believe that the hornworts may represent an intermediate stage in the evolution of the mosses from liverwort like ancestors.

Bryophyta (mosses) grow worldwide in habitats that range from very wet to extremely dry. More than 24,000 species have been described. Unlike the liverworts and hornworts, mosses often have erect stems. Their spore cases are usually borne at the end of long stems called setae. Some are so small that a microscope is needed to see them, but a few may be more than one foot (30 cm) long.

Psilotophyta (whisk ferns) are the most primitive living plants that have vascular tissues-specialized tissues for the transport of water and food. There are only five species. The leaves of the whisk ferns are very small and the stems have a distinctly forked, branching pattern,. Fossils of this group date from more than 400 million years ago.

Microphyllophyta (club mosses) are found in a wide  range of habitats worldwide. Neraly 1,200 species are known. These plants differ from the Psilophyta in that they have transport tissues in their leaves. They also have specialized leaves, called sporophylls, that produce the reproductive spores. It is these sporophylls that resemble clubs and give this group its name.

Equisetophyta (horsetails) grow in relatively moist to very wet habitats in many parts of the world. Today there are only about 20 species, most of which grow to only a few feet in height. About 400 million years ago, however, there were many more species, and some grow to be trees that were more than 50 ft. (15 meters) tall. The leaves of the horsetail rushes are very small; most of the food production occurs in the green stems. Spores are produced in cones that are borne at the ends of stems.

Pteridophyta (ferns) are found in nearly all land ecosystems worldwide. They range in size from small herbs to large trees. More than 10,000 species have been described. Ferns differ from more primitive land plants in that they have well-developed leaves of the tree ferns are the largest and most complex in the plant kingdom. Ferns produce by means of spores produced in specialized capsules on the underside of certain leaves.

Cycadophyta (cycads) are the most primitive plants that reproduce by means of seeds. There are about 100 species, which grow primarily in wet tropical regions. Botanists believe that cycads evolved from fernlike ancestors more than 300 million years ago. About 280 to 70 million years ago these plants were quite common. Pollen is produced in cones on male plants and is carried by winds to female cones, which are on separate plants. When pollinated, ovules develop into seeds that germinate to give rise to new plants.

Ginkgophyta (ginkgo) includes only one species, which no longer grows in the wild, though it is cultivated worldwide as a shade tree. Its native habitat was the deciduous forests of China. Seventy million years ago, forests of ginkgo grew across much of Asia and North America. The ginkgo has flattened broad leaves. Because its ovules are naked, or not surrounded by a fruit, botanists consider the ginkgo to be a relative of the conifers.

Coniferophyta (conifers) grow worldwide. There are about 550 species. Pollen and ovules are exposed, or naked. The leaves of many species are needlelike, but some species have broad leaves. Most conifers keep their leaves year-round and are said to be evergreen, though some are deciduous and lose their leaves in the winter.

Gnetophyta (Gnetum and Ephedra) occur in diverse habitats around the world. There are 71 known species. Their structure resembles that of flowering plants. Although their ovules are exposed like those of the conifers, they are produced in structures that bear some resemblance to flowers. Few fossils are known from this division, and scientist are uncertain about which plant are the closest relatives of the Gnetophytes.

Anthophyta (flowering plants), also called Magnoliophyta, are the most widespread land plants. About 400,000 species have been described, but scientist suspect that the actual number of species may be twice that figure. Members range in size from tiny duckweeds to giant redwoods. This division is made up of monocotyledons and the dicotyledons. Unlike all other seed plants, the flowering plants produce ovules that are enclosed in a fleshy ovary. After fertilization, the ovules develop into seeds and the ovary becomes the fruit. The fruit provides protection for the developing seed and may also be crucial in seed dispersal. While most conifers depend on wind for pollination, the colors and the nectar of flowers attract insects, which then carry pollen from one flower to another.