Glossary of Plant Systematics (1st ed.) by Simpson (2006)
- An indivisual member or segment of the calyx, typically green, leaflike, and functioning to protect the young flower. (flower part, perianth part)
Glossary of "Life (9th ed.)" by Sadava et al. (2011)
- One of the outermost structures of the flower, usually protective in function and enclosing the rest of the flower in the bud stage.
- Sadava, D., Hillis, D. M., Heller, H. C. & Berenbaum, M. R. 2011. Life: The Science of Biology, 9th ed. -xliv + 1266 pp. Sinauer Associates, Inc., Sunderland.