| Cleomaceae | |
|---|---|
 | |
| Polanisia erosa | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Brassicales |
| Family: | Cleomaceae Bercht. &J.Presl[1] |
| Genera[2] | |
TheCleomaceae are a small family offlowering plants in the orderBrassicales, comprising about 220 species in two genera,Cleome andCleomella.[2] These genera were previously included in the familyCapparaceae, but were raised to a distinct family whenDNA evidence suggested the genera included in it are more closely related to theBrassicaceae than they are to the Capparaceae. TheAPG II system allows for Cleomaceae to be included in Brassicaceae.[3] Cleomaceae includes C3, C3–C4, and C4 photosynthesis species.[4]
In 1994, a group of scientists includingWalter Stephen Judd suggested to merge theCapparaceae (which at that time included the Cleomaceae) with the Brassicaceae. Early DNA-analysis showed that the Capparaceae - as defined at that moment - wereparaphyletic, and others suggested to assign the genera closest to the Brassicaceae to the Cleomaceae.[5] The Cleomaceae and Brassicaceae diverged approximately 41 million years ago.[6] All three families have consistently been placed in one order (variably called Capparales orBrassicales).[5] TheAPG II system merged Cleomaceae and Brassicaceae. Other classifications have continued to recognise the Capparaceae, but with a more restricted circumscription, either includingCleome and its relatives in the Brassicaceae or recognizing them in the segregate family Cleomaceae. TheAPG III system has recently adopted this last solution, but this may change as a consensus arises on this point. Current insights in the relationships of the Brassicaceae, based on a 2012 DNA-analysis, are summarized in the following tree.[7]
| core Brassicales |
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Two genera are currently accepted,Cleome with 199 species, andCleomella with 22 species.Plants of the World Online considersOxystylis,Peritoma, andWislizenia synonyms ofCleomella.[2]
Cleomaceae are mostlyannual, sometimesperennialherbaceous plants, seldom shrubs or small trees, and some arelianas. Most of them haveglands, a character setting them apart from the relatedCapparaceae, and containresins, and may have an aromatic or foetid smell. Thealternately set leaves, havestalks and never form a sheath around the stem. The leaves are alwayspalmately compound, mostly with three to seven leaflets, rarely with justone leaflet. At the base of the leafstalk sit scaly, leafy or spinystipules, a difference with itssister groupBrassicaceae that consistently lack stipules, although a pair of glands can sometimes be present at the base of the leaf stalk. Hairs and papillae may be present.[8]
The flowers of Cleomaceae are somewhat to stronglybilateral symmetric. There are mostly four, sometimes two or six, free or mergedsepals, that may be shed quickly or remain, are overlapping in the bud or are already separate. Thecorolla consists of mostly four, sometimes two or sixpetals that have distinctiveclaws and limbs, free or with merged limbs. Thestamens may be placed on the level of insertion of theperianth or on a stalk, raising the bases of the stamens above the perianth. This occurs for instance inGynandropsis gynandra. There are four simple stamens or branched in four groups of up to 12 stamens each that have a common base, and are free from the petals. When there are groups of stamens, theanthers mature from the middle outwards. The base of the stamens may or may not be fused with thefemale parts in the centre of the flower. Thefilaments may be of equal length or strongly differ, and all may carry anthers, but infertilestaminodes may also occur. The anther releases thepollen through slits stretching along its length. The ovary is positioned above the perianth and theandroecium (a so-calledsuperior ovary), consists of two fully mergedcarpels, and contains onecavity that may be divided in two by a partition (orreplum). Between ten and fiftyovules (future seeds) are set along the margins of each of the carpels. As the fruit ripens, a stalk (orgynophore) develops. The dry fruit opens with two valves. When the fruit has a replum, it has the same basic morphology as the Brassicaceae (calledsilicula or siliqua), and this sets it apart from the Capparaceae, that have acapsule.[8]
