What ovarian structure forms at the beginning of the secretory phase, encouraging its progress, and then degenerates just before menses?

Corpus Luteum is the ovarian structure that will form at the beginning of the secretory phase in which it would eventually disintegrate before menstruation. However, it would only fail to regenerate once a fertilised egg was formed thus starting the pregnancy which it will be involved and also ovulation.

I think she should try the experiment one set with fertilizer, and one without. The negative control group would be the set of rose bushes grown without the fertilizer, but under the exact same conditions as the experimental group. Then, if a difference is seen you can be sure it's accurate, since you tested with and without fertilizer under the same conditions. Sorry if i am wrong, I am not completly sure about this one. Again I might be wrong so sorry in advance.