The Collaborative International Dictionary of English v.0.48:
Archegonium \Ar`che*go"ni*um\, n. [NL., fr. Gr. ? the first of a race.] (Bot.) The pistillidium or female organ in the higher cryptogamic plants, corresponding to the pistil in flowering plants. [1913 Webster]WordNet (r) 3.0 (2006):
archegonium n 1: a female sex organ occurring in mosses, ferns, and most gymnosperms