The dicotyledons, also known as dicots, was a grouping formerly used for the flowering plants whose seed typically has two embryonic leaves or cotyledons. There are around 199,350 species within this group. Flowering plants that were not dicotyledons were called monocotyledons, typically having one embryonic leaf.
Dicotyledons are not a monophyletic group, and therefore the names "dicotyledons" and "dicots" are paraphyletic terms. However, the vast majority of "dicots" do form a monophyletic group called the eudicots or tricolpates. These may be distinguished from all other flowering plants by the structure of their pollen. Other dicotyledons and monocotyledons have monosulcate pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms, the pollen having three or more pores set in furrows called colpi.
Traditionally the dicots have been called the Dicotyledones (or Dicotyledoneae), at any rank. If treated as a class, as in the Cronquist system, they may be called the Magnoliopsida after the type genus Magnolia. In some schemes, the eudicots are treated as a separate class, the Rosopsida (type genus Rosa), or as several separate classes. The remaining dicots (palaeodicots) may be kept in a single paraphyletic class, called Magnoliopsida, or further divided.
Some information in this copy may have been obtained from the online resource: Wikipedia: The Free Encyclopedia.
Learn more: en.wikipedia.org/wiki/Dicotyledon