Flowering plants are usually treated as a division, formerly called the Angiospermophyta or Anthophyta, but now called Magnoliophyta after the type genus Magnolia. The main split within the Division Magnoliophyta is between the dicotyledons and monocotyledons (or dicots and monocots for short). The names come from the number of embryonic leaves, called cotyledons, found within the seed, but there are other notable differences (see "How to distinguish a monocot from a dicot"). The dicots are now considered a paraphyletic group, though most belong to a monophyletic subgroup called the eudicots or tricolpates.
The classification of flowering plants has undergone considerable revision as ideas about their relationships change. The classification given by Arthur Cronquist (1981) is widely used. Although many of the proposed groupings have been questioned, a general consensus has started to emerge about what the breakdown of the Magnoliophyta should look like.
The most common families of flowering plants, in order of number of species, are:
- Asteraceae (daisy family): 25,000 species
- Orchidaceae (orchid family): 18,000
- Fabaceae (pea family): 17,000
- Poaceae (grass family): 9,000
- Rubiaceae (coffee family): 7,000
- Euphorbiaceae (spurge family): 5,000
- Cyperaceae (sedge family): 4,000