Dicotyledon

"Dicot" redirects here. For the band, see Dicot (band).

Magnoliopsida (Dicotyledons)
Magnolia flower
Scientific classification
Kingdom: Plantae Phylum: Magnoliophyta Class: Magnoliopsida* Brongniart
Included groups
Eudicot Magnoliid Amborella Nymphaeales Austrobaileyales Chloranthales Ceratophyllum
Excluded groups
Monocot

Young castor oil plant showing its prominent two embryonic leaves (cotyledons), that differ from the adult leaves.

The dicotyledons, also known as dicots, are a group of flowering plants whose seed typically has two embryonic leaves or cotyledons. There are around 199,350 species within this group.^[1] Flowering plants that are not dicotyledons are monocotyledons, typically having one embryonic leaf.

Dicotyledons are not a monophyletic group, and therefore the names "dicotyledons" and "dicots" are, strictly speaking, deprecated. 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.

Compared to Monocotyledons

Aside from cotyledon number, other broad differences have been noted between monocots and dicots, although these have proven to be differences primarily between monocots and eudicots. Many early-diverging dicot groups have "monocot" characteristics such as scattered vascular bundles, trimerous flowers, and non-tricolpate pollen. In addition, some monocots have dicot characteristics such as reticulated leaf veins.

Feature	In monocots	In dicots
Number of parts of each flower	in threes (flowers are trimerous)	in fours or fives (tetramerous or pentamerous)
Number of furrows or pores in pollen	one	three
Number of cotyledons (leaves in the seed)	one	two
Arrangement of vascular bundles in the stem	scattered	in concentric circles
Roots	are adventitious	develop from the radicle
Arrangement of major leaf veins	parallel	reticulate

Classification

APG (Angiosperm Phylogeny Group) vs. Cronquist Classification

The following lists are of the orders formerly placed in the dicots, giving their new placement in the APG-system and that under the older Cronquist system, which is still in wide use.

APG II (polyphyletic)	Cronquist system (classis Magnoliopsida)
Amborellaceae Chloranthaceae Nymphaeaceae [+ Cabombaceae] Austrobaileyales Ceratophyllales Magnoliids Canellales Laurales Magnoliales Piperales eudicots Buxaceae [+ Didymelaceae] Sabiaceae Trochodendraceae [+ Tetracentraceae] Proteales Ranunculales Core eudicots Aextoxicaceae Berberidopsidaceae Dilleniaceae Gunnerales Caryophyllales Santalales Saxifragales rosids Aphloiaceae Geissolomataceae Ixerbaceae Picramniaceae Strasburgeriaceae Vitaceae Crossosomatales Geraniales Myrtales Eurosids I Zygophyllaceae [+ Krameriaceae] Huaceae Celastrales Cucurbitales Fabales Fagales Malpighiales Oxalidales Rosales Eurosids II Tapisciaceae Brassicales Malvales Sapindales Asterids Cornales Ericales Euasterids I Boraginaceae Icacinaceae Oncothecaceae Vahliaceae Garryales Gentianales Lamiales Solanales Euasterids II Bruniaceae Columelliaceae [+ Desfontainiaceae] Eremosynaceae Escalloniaceae Paracryphiaceae Polyosmaceae Sphenostemonaceae Tribelaceae Apiales Aquifoliales Asterales Dipsacales	Magnoliidae (mostly basal dicots) Magnoliales Laurales Piperales Aristolochiales Illiciales Nymphaeales Ranunculales Papaverales Hamamelidae Trochodendrales Hamamelidales Daphniphyllales Didymelales Eucommiales Urticales Leitneriales Juglandales Myricales Fagales 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 Linales Polygalales Sapindales Geraniales Apiales Asteridae Gentianales Solanales Lamiales Callitrichales Plantaginales Scrophulariales Campanulales Rubiales Dipsacales Calycerales Asterales
Note: "+ ..." = optionally separate family, that may be split off from the preceding family.

Dahlgren and Thorne systems

In the Dahlgren and the Thorne systems, the name Magnoliidae is used for the dicotyledons. This is also the case in some of the systems derived from the Cronquist system. For each system, only the superorders are listed. The sequence of each system has been altered to pair corresponding taxa, although circumscription of superorders with the same name is not always the same. The Thorne system (1992) is the version of the system as depicted by Reveal.

Comparison of the Dahlgren and Thorne systems

Dahlgren system	Thorne system
Magnolianae Ranunculanae	Magnolianae Rafflesianae
Nymphaeanae	Nymphaeanae
Caryophyllanae	Caryophyllanae
Theanae Plumbaginanae Polygonanae Primulanae Ericanae	Theanae
Malvanae	Malvanae
Violanae	Violanae
Rosanae	Rosanae
Proteanae	Proteanae
Myrtanae	Myrtanae
Rutanae	Rutanae Celastranae Geranianae
Santalanae	Santalanae
Balanophoranae	Santalanae
Asteranae	Asteranae
Solananae	Solananae
Cornanae Vitanae	Cornanae Aralianae
Loasanae	Loasanae
Dicotyledons	Gentiananae Lamianae	Gentiananae

References

1. ^ Hamilton, Alan; Hamilton, Patrick (2006), Plant conservation : an ecosystem approach, London: Earthscan, pp. 2, ISBN 9781844070831, http://books.google.com/?id=P6m0OTheY8sC&printsec=frontcover#PPA2,M1