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).
Alternation of Generations. All Embryophytes and some algae undergo an Alternation of Generations. Each generation of offspring has a different ploidy than the generation before it. Generations alternate from diploid to haploid to diploid to haploid, etc. sporophyte (2n) --> gametophyte (n) --> sporophyte (2n) --> gametophyte (n) --> sporophyte (2n) etc... In short: 1. a haploid (n) gametophyte generates gametes (n) via mitosis 2. gametes fuse to form a diploid (2n) zygote 3. zygote grows mitotically into the sporophyte (2n) 4.