Angiosperms represent the largest class of plant life on Earth, or approximately 90 percent of all existing plants. Angiosperms are seed plants that reproduce via flowers, in contrast with conifers, seed plants that reproduce via cones and other similar structures. The flowers in your garden, the trees producing the fruit you eat, the colorful ornamentals found in botanical gardens throughout the world–all of them belong to the angiosperm class.
Monocots are one of the two major types of angiosperm. Botanists define a monocot, or monocotyledon, plant by its seed leaves. The cotyledon, or seed leaf, is one of the first parts of a plant to emerge from the soil during germination, and plays an important role in plant reproduction. Monocots, as the name implies, have only one seed leaf. Other features of monocots include veins in the leaves, flower parts in multiples of three, and scattered vascular bundles within the plant. Corn, grass and palm trees are monocots.
Dicots are the other major type of angiosperm. Botanists define dicots as plants with two seed leaves. Other distinguishing features of dicot angiosperms are complex, netlike patterns of veins in leaves, flower parts in multiples of four or five, and vascular bundles in distinct rings within the plants. Among the best-known dicots are roses, sunflowers, cacti, and apple and cherry trees. The dicotyledon group of angiosperms comprises the bulk of species in the class.
The Largest Angiosperm Families
Angiosperms are divided into families, each of which constitutes a different type of angiosperm. The three largest angiosperm families make up the bulk of angiosperm types. The sunflower family (asteraceae) contains nearly 24,000 species of plants ranging in size from those with flower heads a fraction the size of a penny to those with flower heads larger than a human head. The orchid family of tropical flowering plants contains approximately 20,000 species. The legume, or pea, family of plants is the third-largest of the angiosperm families and contains about 18,000 species of plants.
Other Families of Angiosperms
Other families of angiosperms include the begonia family (begoniaceae), to which more than 900 species belong; the fig family (moraceae), which has more than 800 species; the rose family (rosaceae), to which more than 2,000 species belong; the coffee family (rubiaceae), to which more than 1,500 species belong; the nightshade family (solanaceae), which has more than 1,400 species; and the heath family (ericaceae), to which more than 1,700 species belong, including rhododendrons.