- (in Orchidaceae) the central petal, which is often lobed or spurred, and hence differs from the other two petals;
- (in Zingiberaceae) a large petaloid, sometimes lobed, object which together with the stamen forms the androecium.
Copyright: Mike Bingham, Annette Willemen, Bart Wursten, Petra Ballings and Mark Hyde, 2011-17
Bingham, M.G., Willemen, A., Wursten, B.T., Ballings, P. and Hyde, M.A.
. Flora of Zambia: Glossary details: labellum.
http://www.zambiaflora.com/speciesdata/glossary-display.php?glossary_id=393, retrieved 29 March 2017