SUMMARY The ascospores of Podospora anserina (Ces.) Rehm are delimited by a double membrane system. The primary spore wall develops within this, the outer part of the double membrane being pushed out to form the spore mem- brane and the inner part forming the plasmalemma of the spore. Starting in the middle of the matrix of the expanding primary wall, a secondary wall is laid down and gradually extends to the outer periphery of the spore wall. Later, a thick tertiary wall is formed at the inner side of the secondary wall by blocks of electron-dense material between which channels of the primary wall matrix remain. This is the pigmented layer of the spore wall. On the innermost side of the spore wall, a part of the original primary wall remains. The primary appendage at the base of the spore arises as part of the spore initial, but, after it has been cut off by a septum, its contents degenerate and it is bounded only by the primary and secondary wall layers. The secondary appendages, formed at the apex of the spore and at the bottom of the pri- mary appendage, are considered to be actively growing processes bounded by the spore membrane.