The aura can be in the form of prismatic colors, flashes of light, and sometimes stars. They usually last about 20 minutes and then go away. If these flashes or lines of light occur without a headache, it is called an ophthalmic migraine, or a migraine without a headache.
In gymnosperms and flowering plants, the megaspore is produced inside the nucellus of the ovule. During megasporogenesis, a diploid precursor cell, the megasporocyte or megaspore mother cell, undergoes meiosis to produce initially four haploid cells (the megaspores).
Remember, a sporophyte is a diploid organism. So in order to produce haploid cells with half the number of chromosomes, meiosis must occur. Meiosis is a type of cell division that cuts the number of chromosomes in a cell in half. In sporophytes, it occurs in structures called sporangia (sporangium is singular).