| Because the egg is retained and fertilized within the archegonium, the early stages of the developing sporophyte are protected and nourished by the gametophytic tissue. |
| Although more than one archegonium may be fertilized, only one gives rise to a viable embryo. |
| The axis of the embryo is inclined to that of the archegonium and may be almost at right angles. |
| An archegonium consists of neck cells and a large egg cell. |
| In the club mosses the zygote divides in a plane at right angles to the axis of the archegonium. |
| The neck of the archegonium is quite long, but does not project above the surface of the prothallium. |
