Dicotyledon

Dicotyledons or dicots are flowering plants whose seed contains two embryonic leaves or cotyledons. Flowering plants, or angiosperms, that are not dicotyledonous are monocotyledonous: having one embryonic leaf. See How to distinguish a monocot from a dicot for other characteristics that separate these two groups.

It is believed that monocots evolved from dicots, and as such the latter form a paraphyletic group, i.e. they include some forms which are as closely related to monocots as they are to the other dicots. The vast majority, however, form a monophyletic group, called the eudicots or tricolpates. These may be distinguished from other flowering plants by the structure of their pollen. Basal dicots and monocots have monosulcate pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms.

Traditionally the dicots have been treated as a class, originally called the Dicotyledoneae, but more recently called class Magnoliopsida after the type genus Magnolia. In some schemes, the eudicots are treated as a separate class Rosopsida (type genus Rosa), or as several separate classes. The remaining dicots may be kept in a single paraphyletic class Magnoliopsida, or further divided. The classification of dicots has undergone considerable revision as our understanding of their relationships has changed, and is still not entirely settled, though a general consensus is emerging.

The following lists are of the orders typical of new classification systems and those under the older Cronquist system, which is still in wide use.

Orders typical of newer systems

Cronquist system

Basal dicots (palaeodicots) Amborellales Nymphaeales Austrobaileyales Chloranthales Ceratophyllales Magnoliid basal dicots (Magnoliidae) Magnoliales Laurales Piperales Aristolochiales Canellales Basal eudicots Ranunculales Buxales Trochodendrales Proteales Gunnerales Berberidopsidales Dilleniales Caryophyllales Saxifragales Santalales Vitales Basal rosids Crossosomatales Geraniales Myrtales Eurosids I Zygophyllales Celastrales Malpighiales Oxalidales Fabales Rosales Cucurbitales Fagales Eurosids II Brassicales Malvales Sapindales Basal asterids Cornales Ericales Euasterids I Garryales Solanales Gentianales Lamiales Unplaced: Boraginaceae Euasterids II Aquifoliales Apiales Dipsacales Asterales

Magnoliidae (mostly basal dicots) Magnoliales Laurales Piperales Aristolochiales Illiciales Nymphaeales Ranunculales Papaverales Hamamelidae Trochodendrales Hamamelidales Daphniphyllales Didymelales Eucommiales Urticales Leitneriales Juglandales Myricales Casuarinales Caryophyllidae Caryophyllales Polygonales Plumbaginales Dilleniidae Dilleniales Theales Malvales Lecythidales Nepenthales Violales Salicales Capparales Batales Ericales Diapensiales Ebenales Primulales Rosidae Rosales Fabales Proteales Podostemales Haloragales Myrtales Rhizophorales Cornales Santalales Rafflesiales Celastrales Euphorbiales Rhamnales Polygalales Sapindales Geraniales Apiales Asteridae Gentianales Solanales Lamiales Callitrichales Plantaginales Scrophulariales Campanulales Rubiales Dipsacales Calycerales Asterales