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Other fossilized finds include a pinecone-like structure with megaspores and some fossilized tree trunks used to estimate the height of the trees, Wang noted.

The tissue at the apex of the megaspore grows slightly above the level of the archegonia, so that the latter come to lie in a shallow depression.

For an account of the further development of the megaspore, and the formation of the egg-cell, from which after fertilization is formed the embryo, see Gymnosperms and Angiosperms.

In both forms cysts containing megaspores and megasporozoites, and others containing microspores and microsporozoites are found, considered as representing sexual differentiation thrown back to the very earliest stages of the life-cycle.

The behaviour of the chromosomes in meiosis or reduction division both in the pollen mother-cells and in the megaspore mother-cells which give rise to the so-called embryo-sac are fully described by Gates.