The same moisture which caused the antheridia to open also brings about the opening of the archegonia.
The archegonia (Fig. 61) should be looked for in the younger plants in the neighborhood of those that bear capsules.
As a rule, too, in the prothallus only one of the archegonia shows any further signs of development.
The archegonia have a shorter neck than those of the ferns, and the neck is straight.
The necks of the archegonia hardly project above the general surface of the thallus.
The sexual organs are borne on the upper surface, and both antheridia and archegonia occur on the same branch (fig. 3, A).
The archegonia are borne at the apex of the main stem or of a lateral branch.
In addition special involucres around the archegonia have arisen independently in several series.
The archegonia are protected by being sunk in depressions of the disk or by a special two-lipped involucre.
The female plant is rather more highly organized, consisting of a short stem bearing a few leaves around the group of archegonia.
The egg-producing organ occurring in bryophytes (such as mosses and liverworts), ferns, and most gymnosperms. The archegonium is a multicellular, often flask-shaped structure that contains a single egg. Compare antheridium.