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).
Mitosis (M) encompasses just one step in the eukaryotic cell cycle: G1 > S > G2 > M > C. Cells grow during the dominant G1 phase. Replication of chromosomes occurs in the S phase. Preparation for mitosis takes place during G2 - replication of organelles and synthesis of microtubules. Interphase includes the combined stages G1, S, and G2.