Labellum (plural: labella) is the Latin diminutive of labium, meaning lip.
The labellum is a modified petal and can be distinguished from the other petals and from the sepals 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. 
Labellum from Phalaenopsis sp
- Bailey, L. H. Gentes Herb. Canna x orchiodes. (Ithaca), 1 (3): 120 (1923).
- Khoshoo, T. N. & Guha, I. Origin and Evolution of Cultivated Cannas. Vikas Publishing House.
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