In plant taxonomy, commelinids (plural, not capitalised) is a name used by the APG III system

APG III system

The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy...

 for a clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 within the monocots, which in its turn is a clade within the angiosperms. The commelinids are the only clade that the APG has informally named within the monocots. The remaining monocots are a paraphyletic unit.

Members of the commelinid clade have cell wall

Cell wall

The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

s containing UV-fluorescent

Fluorescence

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...

 ferulic acid

Ferulic acid

Ferulic acid is a hydroxycinnamic acid, a type of organic compound. It is an abundant phenolic phytochemical found in plant cell wall components such as arabinoxylans as covalent side chains. It is related to trans-cinnamic acid. As a component of lignin, ferulic acid is a precursor in the...

, and many groups possess peculiar crystalloid projections of epicuticular wax

Epicuticular wax

In botany, the plant cuticle is covered by epicuticular wax or bloom mainly consistingof straight-chain aliphatic hydrocarbons with a variety of substituted groups, serving to decrease moisture loss and decay...

.

Classification

The commelinids were first recognized as a formal group in 1967 by Armen Takhtajan

Armen Takhtajan

Armen Leonovich Takhtajan or Takhtajian , was a Soviet-Armenian botanist, one of the most important figures in 20th century plant evolution and systematics and biogeography. His other interests included morphology of flowering plants, paleobotany, and the flora of the Caucasus...

, who named them the Commelinidae and assigned them to a subclass of the monocots. However, by the release of his 1980 system of classification, he had merged this subclass into a larger one no longer considered to be a clade.

The commelinids constitute a well-supported as a clade within the monocots, and this clade has been recognized in all three APG classification systems. The commelinids of APG II (2003) and APG III (2009) contain essentially the same plants as the commelinoids of the earlier APG system

APG system

The APG system of plant classification is the first, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in 1998 by the Angiosperm Phylogeny Group. It was superseded in 2003 by a revision, the APG II system, and then in 2009 by a further...

 (1998).

clade monocots : clade commelinids Commelinids In plant taxonomy, commelinids is a name used by the APG III system for a clade within the monocots, which in its turn is a clade within the angiosperms. The commelinids are the only clade that the APG has informally named within the monocots... : family Dasypogonaceae Dasypogonaceae Dasypogonaceae is a botanical name of a family of flowering plants. Such a family has not been commonly recognized by taxonomists: the plants involved were usually included in the family Xanthorrhoeaceae.... order Arecales (palms) order Commelinales Commelinales Commelinales is the botanical name of an order of flowering plants. It comprises five families: Commelinaceae, Haemodoraceae, Hanguanaceae, Philydraceae, and Pontederiaceae. All the families combined contain over 800 species in about 70 genera; the majority of species are in the Commelinaceae...  (spiderwort, water hyacinth) order Poales Poales Poales is a large order of flowering plants in the monocotyledons, and includes families of plants such as the grasses, bromeliads, and sedges. Sixteen plant families are currently recognized by botanists to be part of Poales....  (grasses, rushes, bromeliads) order Zingiberales Zingiberales Zingiberales is an order of flowering plants. The order has been widely recognised by the taxonomists, at least for the past few decades. This order includes many familiar plants like ginger, cardamom, turmeric, galangal and myoga of the Zingiberaceae or ginger family, and bananas and plantains...  (gingers, banana)	{clade| style=font-size:75%;line-height:75%	label1=commelinids	1= }}
The current phylogeny Phylogenetics In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices... and composition of the commelinids.