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).
Single-celled eukaryotes, such as amoeba and yeast, use mitosis to reproduce asexually and increase their population numbers. Multicellular eukaryotes use mitosis to grow or heal injured tissues. The second type of cell division, meiosis, is a specialized form of cell division that occurs in organisms that reproduce sexually (that is, by combining the unique genetic information of two parents). Meiosis produces reproductive cells, such as sperm cells, egg cells and spores from plants and fungi.