Definition of "calyptrae"

On fertilization, the archegonia form obyriform calyptrae that are distinctly narrowed at base to form a stalk or peduncle; this does not occur in other Hepaticae.

1992, Rudolf M[athias] Schuster, The Hepaticae and Anthocerotae of North America: East of the Hundredth Meridian, volume V, New York, N.Y.: Columbia University Press, page 5