The biochemical and physical duet of the mother and the fetus in the formation of the placenta is one of the most carefully orchestrated phenomena in fetal development. It represents the cooperation of two distinct individuals to form a single structure that protects one and enables the genes of the other to live on.
This cycle is known as alternation of generations. The spores of seed plants, however, are produced internally and the megaspores, formed within the ovules and the microspores are involved in the formation of more complex structures that form the dispersal units, the seeds and pollen grains.
Sporangia (Clustered in sori). The sporangia is the structure which produces spores. In ferns the sporangia are usually aggregated into particular bigger structures, if you turn over a fern frond and you might see lines and those are aggregations of the sporangia.pores. So a spore is the product of meiosis. In ferns its tiny, if you think of a ruler and think how big a centimetre is and divide that by ten then you've got a millimetre and then divide that by ten again and then halve it that is about the size of the spore.