Dicotyledons, also known as dicots, are one of the two groups into which all flowering plants, or angiosperms, are divided. There are about 200,000 species within this group, including most garden plants like magnolias, roses and geraniums. Pecan trees, water oaks, mistletoe, sassafras and poison ivy also are dicots.
Dicotyledons have two embryonic leaves, or cotyledons. Cotyledons are seed leaves produced by the embryo that absorb nutrients packaged in the seed until the plant is able to produce its first true leaves and begin photosynthesis. Monocotyledons have only one cotyledon. Monocotyledons consist of the rest of the angiosperms, about 60,000 species in all.
The number of cotyledons found in the embryo is the basis for differentiating the two classes of angiosperms, but they have many more distinguishing characteristics. Monocotyledons are monosulcate, meaning they have pollen with a single furrow or pore. Dicotyledons are triporate, meaning they have pollen with three pores or furrows. The number of petals, stamens or other parts of the flower is often divisible by three in a monocotyledon, but this number is often divisible by four or five in a dicotyledon.
Monocotyledons have many major leaf veins that run parallel the length of the leaf. Dicotyledons have this as well as numerous axillary veins weaving through these major leaf veins.