Editing Labellum (botany) (section)

{{Short description|Botanical term}}
{{other uses|Labellum (disambiguation)}}
[[Image:Cypripedium reginae.jpg|thumb|right|[[Showy lady slipper]] (''Cypripedium reginae'') has a pink '''labellum''']]
[[Image:Labelle orchidee.png|thumb|right|'''P:''' Petalum<br />'''S:''' Sepalum<br />'''L:''' '''Labellum''']]
In botany, the '''labellum''' (or '''lip''') is the part of the flower of an [[Orchidaceae|orchid]] or ''[[Canna (plant)|Canna]]'', or other less-known genera, that serves to attract [[insect]]s, which [[pollination|pollinate]] the flower, and acts as a landing platform for them.

''Labellum'' (plural: ''labella'') is the Latin diminutive of ''labrum'', meaning lip.

The labellum is a modified petal and can be distinguished from the other [[petal]]s and from the [[sepal]]s by its large size and its often irregular shape. It is not unusual for the other two petals of an orchid flower to look like the sepals, so that the labellum stands out as distinct.<ref>[[Liberty Hyde Bailey|Bailey, L. H.]] ''Gentes Herbarum: Canna x orchiodes''. (Ithaca), 1 (3): 120 (1923); Khoshoo, T. N. & Guha, I. ''Origin and Evolution of Cultivated Cannas.'' Vikas Publishing House.</ref>

In orchids, the labellum is the modified median petal that sits opposite from the fertile [[anther]] and usually highly modified from the other [[perianth]] segments. It is often united with the [[column (botany)|column]] and can be hinged or movable, facilitating pollination. Often, the orchid labellum is divided into three or more lobes. Some have modified fleshy lumps on the upper surface generally referred to as the '''callus''' (plural: ''calli''), with some being divided into multiple ridges or a central '''keel'''. When the callus is flat and broad, it is sometimes called a plate, which can have fringed margins. The callus can be highly modified with striking colors that may aid in pollinator deceit and mimicry.<ref name="Dressler 1993">Dressler, R.L. 1993. ''Phylogeny and Classification of the Orchid Family''. Portland, Oregon: Dioscorides Press. pp. 29-30.</ref><ref name="Kurzweil and Kocyan">{{cite book |last1=Kurzweil |first1=Hubert |last2=Kocyan |first2=Alexander |editor1-last=Kull |editor1-first=Tiiu |editor2-last=Arditti |editor2-first=Joseph |title=Orchid Biology: Reviews and Perspectives, VIII |publisher=Kluwer Academic Publishers |year=2002 |pages=83–138 |chapter=Ontogeny of orchid flowers |isbn=1-4020-0580-6}}</ref>

The labellum in orchids is often large and complex enough that terminology describing relative positions for structures on it becomes useful: the '''hypochile''' is the basal portion nearer the connection with the rest of the flower, the '''mesochile''' is the middle portion, and the '''epichile''' is the distal portion.<ref name="Dressler 1993"/>