In botany, the labellum (or lip) is the part of the flower of an

orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering ...

or '' Canna'', 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 of ...

s, which

pollinate Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...

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 Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corolla''. Petals are usually ...

s 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 The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...

and usually highly modified from the other

perianth The perianth (perigonium, perigon or perigone in monocots) is the non-reproductive part of the flower, and structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla (petals) or tepals when ...

segments. It is often united with the

column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member. ...

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 ''Phalaenopsis'' (), also known as moth orchids, is a genus of about seventy species of plants in the family Orchidaceae. Orchids in this genus are monopodial epiphytes or lithophytes with long, coarse roots, short, leafy stems and long-lasting ...

'' hybrid File:Orchis italica 042.JPG, ''

Orchis italica ''Orchis italica'', the naked man orchid or the Italian orchid, is a species of orchid native to the Mediterranean Basin. It gets its common name from the lobed lip (labellum) of each flower which mimics the general shape of a naked man. In It ...

'', the naked man orchid, showing a labellum divided into several lobes File:Laelia superbiens Orchi 002.jpg, Labellum of the orchid ''

Laelia superbiens ''Laelia superbiens'' is a species of orchid native to Mexico, Guatemala and Honduras Honduras, officially the Republic of Honduras, is a country in Central America. The republic of Honduras is bordered to the west by Guatemala, to the s ...

'', showing five wavy ridges of the callus File:Chiloglottis aff. jeanesii labellum.jpg, Labellum with highly modified calli in a species of ''

Chiloglottis ''Chiloglottis'', commonly known as wasp orchids, ant orchids or bird orchids, is a genus of about 25 species of flowering plants in the orchid family, Orchidaceae and is found in eastern Australia and New Zealand. Wasp orchids are terrestrial ...

References

{{Commons, Labellum (Orchidaceae), Labellum Plant morphology Orchid morphology

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See also

References