Synsepal

A synsepal is a floral structure formed by the partial or complete fusion of two or more sepals.^[1] Such sepals are said to be synsepalous or gamosepalous.^[2]

It is common among lady's slipper orchids (Cypripedioideae) that the two lateral sepals are connate to form a synsepal in the outer whorl. This is located directly behind the pouch, opposite the upward-pointing dorsal sepal.

Synsepals may be bifid, i.e. divided into two equal lobes, or forked and divided in two by a deep cleft.

References

1. Wu, Zheng-yi; Raven, Peter H., eds. (2009). Flora of China: Orchidaceae. Flora of China. Vol. 25. Science Press and Missouri Botanical Garden Press. p. 3. ISBN 978-1-930723-90-0. OCLC 223628675.
2. Eckel, P. M. "A Grammatical Dictionary of Botanical Latin". Missouri Botanical Garden. Archived from the original on 1 May 2021. Retrieved 9 October 2024.