MONOCOTYLEDON

byname Monocot, any plant of the class Liliopsida (Monocotyledoneae), the smaller of the two great groups (the larger of which is the Magnoliopsida, or dicotyledons) of flowering plants, or angiosperms. There are approximately 50,000 species of monocots. Lilies, orchids, palms, irises, and grasses are monocots. Most of them are distinguished by the presence of only one seed leaf, or cotyledon, in the embryo contained in the seed. Monocots most often have flower parts (sepals, petals, stamens, and so on) based on a plan of three or multiples thereof. The leaves are parallel-veined in most, either from the base or from a stout central midrib. In the stem the water- and food-conducting vessels are usually arranged in scattered bundles. About 10 percent of all monocots are woody; some, such as palms and bamboos, show a continual increase in stem diameter as a result of cell enlargement or the production of cells from internal cells (rather than from a cambium layer as in the dicots). Most monocots are herbaceous. Taproots are uncommon; fibrous roots predominate. Stem branching is uncommon. The microscopic pores (stomates) in the leaf surfaces are usually arranged in parallel rows. The pollen grains of monocots have one germinal furrow, or pore, the monocolpate condition.