In botany, the labellum (or lip) is the part of the flower of an
orchid or ''
Canna
Canna may refer to:
Places
* Canna, Western Australia, a locality in the Shire of Morawa, Australia
* Canna, Calabria, a ''comune'' in the Province of Cosenza, Italy
* Cannae, a ''frazione'' in the Province of Barletta-Andria-Trani, Apulia, Ita ...
'', or other less-known genera, that serves to attract
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...
s, which
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
petals and from the
sepal
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined ...
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.
[ 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.]
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 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.
[Dressler, R.L. 1993. ''Phylogeny and Classification of the Orchid Family''. Portland, Oregon: Dioscorides Press. pp. 29-30.]
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.
Gallery
File:Labelle.JPG, Labellum of a '' Phalaenopsis'' hybrid
File:Orchis italica 042.JPG, '' Orchis italica'', the naked man orchid, showing a labellum divided into several lobes
File:Laelia superbiens Orchi 002.jpg, Labellum of the orchid '' Laelia superbiens'', showing five wavy ridges of the callus
File:Chiloglottis aff. jeanesii labellum.jpg, Labellum with highly modified calli in a species of '' Chiloglottis''
See also
*
Glossary of botanical terms
References
{{Commons, Labellum (Orchidaceae), Labellum
Plant morphology
Orchid morphology