DICOTYLEDON

byname Dicot, any plant of the class Magnoliopsida (magnoliatae, Dicotyledones), the larger of the two great groups (the smaller is the Liliopsida, or Monocotyledones) of flowering plants, or angiosperms. There are about 175,000 known species of dicots. Most common garden plants, shrubs and trees, and broad-leafed flowering plants such as magnolias, roses, geraniums, and hollyhocks are dicots. Most dicots are characterized by the presence of a pair of seed leaves, or cotyledons, in the embryo contained in the seed. Dicots typically also have flower parts (sepals, petals, stamens, etc.) based on a plan of four or five, or multiples thereof, although there are exceptions. The leaves are net-veined in most, which means the vessels that conduct water and food show a meshlike pattern. In the stems the vessels are usually arranged in a continuous ring near the stem surface. About 50 percent of all dicot species are woody; they show an annual increase in stem diameter as a result of the production of new tissue by the cambium, a layer of cells that remain capable of division throughout the life of these plants. Branching of stems is common, as are taproots. The microscopic pores (stomates) on the leaf surfaces are usually scattered and are in various orientations. The pollen grains typically have three germinal furrows or pores (tricolpate condition), except in the more primitive families.