Editing Tepal (section)

== Origin ==
[[Image:Zanlophator1a.UME.jpg|right|200px|thumb|A ''[[Lilium]]'' flower showing the six '''tepals''': the outer three are sepals and the inner three are petals.]]
Undifferentiated tepals are believed to be the ancestral condition in [[flowering plant]]s. For example, ''[[Amborella]]'', which is thought to have separated earliest in the evolution of flowering plants,<ref>{{Cite journal | last1 = Ronse De Craene | first1 = L. P. | title = Are Petals Sterile Stamens or Bracts? The Origin and Evolution of Petals in the Core Eudicots | doi = 10.1093/aob/mcm076 | journal = Annals of Botany | volume = 100 | issue = 3 | pages = 621–630 | year = 2007 | pmid =  17513305| pmc =2533615 }}</ref> has flowers with undifferentiated tepals. Distinct petals and sepals would therefore have arisen by differentiation, probably in response to animal [[pollination]]. In typical modern flowers, the outer or enclosing [[whorl]] of organs forms sepals, and is specialised for protection of the flower bud as it develops, while the inner whorl forms petals, which attract [[pollinator]]s.

Tepals formed by similar sepals and petals are common in [[monocotyledon]]s, particularly the "[[lilioid monocot]]s". In [[tulip]]s, for example, the first and second whorls both contain structures that look like petals. These are fused at the base to form one large, showy, six-parted structure (the perianth). In [[Lilium|lilies]] the organs in the first whorl are separate from the second, but all look similar, thus all the showy parts are often called tepals. Where sepals and petals can in principle be distinguished, usage of the term "tepal" is not always consistent – some authors will refer to "sepals and petals" where others use "tepals" in the same context.

In some plants the flowers have no petals, and all the tepals are sepals modified to look like petals. These organs are described as [[petaloid]], for example, the sepals of [[hellebore]]s. When the undifferentiated tepals resemble petals, they are also referred to as "petaloid", as in [[petaloid monocots]], orders of monocots with brightly coloured tepals. Since they include [[Liliales]], an alternative name is lilioid monocots.